It's the smallest chance for the biggest to be best these days although it's a comforting and simultaneously ludicrous thought that these overblown FX festivals called Hollywood summer movies could actually have some social merit and, dare I say it, change lives? Hmm. There's too much money at stake to take any real narrative chances with budgets skyward of two hundred million. So let me chisel out the five franchise commandments from Mount Skynet, sorry, Sinai.

Thou shalt provide more of the same but different.

Sequels these days are almost guaranteed to simply make things bigger which is never really satisfying without the heart that lead to the passion that started the whole thing off. This is, I think, why Jonathan Mostow's T3 feels weaker than the others in the series. But McG has pulled it off – it's bigger but it also has a heart (in one since, literally). Tick No. 1. I have no idea why Harry Knowles was so pissed off. When can a movie not amount to personal expectation? Answer? All the time. Harry wanted his John Connor mythology satisfied. Ah, well.

Thou shalt never 'end' the franchise.

Well, McG has played by that rule so in an approximation of John Connor's words, "a battle was won, not the war..." Tick No. 2. The implication is that there are many more battles/sequels to fight/shoot. No ribbon tying for Cameron's ongoing conflict.

Thou shalt never kill the icons from the franchise.

Metallic icons, all versions, can always return, be re-made, reborn. (There is a nice 1984 T1 moment in the movie that technically looks terrific). No problem bringing back machines but what of the human stars? If John Connor dies, the franchise takes a big hit (no big spoilers in this review but that's No. 3 ticked or un-ticked but it is attended to). Nitpickers note; Alien Resurrection didn't count as cloning was believable technology in that particular future. And the clue's in the title.

Thou shalt subtly weave in any famous lines justifiably.

"I'll be back," and "Come with me if you want to live," both feature and very nicely too. It's a nod to the past but without any fanfare or knowing wink. Tick No. 4. Heaven knows how this movie would have panned out if Jeffrey "I-Must-Reference-All-Movies-Ha-Ha-Ha" Katzenberg was the exec. He can't handle the truth... Jesus.

Thou shalt respect what came before.

McG and the film-makers have stayed extremely faithful to the mythology but as this one is set after Judgement Day and before Connor sends Kyle back to shimmy with his mom, the designers can reinterpret the visual palette and the movie's look is suitably drained of colour. It's got a desert storm feel and it's right for the story they're telling. Respect is noted. T3 is all but ignored seen by most people as the weakest and most cynically profit motivated of the, by then, trilogy. But as a stand-alone war movie with the foundations of what James Cameron could never have afforded to shoot in the first one, McG has done a pretty fine job. And there are technical scenes in this film that are startlingly good but never placed front and centre with the subtext, "Look what I can do, Ma!" I had expected a literal and a metaphorical car crash of a film and I was very happily surprised to be wrong. Pop videos and Charlie's Angels need not be a director's type-casted future despite proficiency in those areas. It fair grinds my gears when I'm passed over for a job because of what I've done most supposedly disqualifies me. Kubrick never had to put up with that pigeonholing crap.

Terminator Salvation is a movie about the perseverance of the human spirit (and fuck-off robots beating eight shades of shit out of people, let's not get too philosophical here). Let's also remind ourselves that humanity is at risk and that, at the very least, gives an audience a species to root for. Now Christian Bale has come in for some flak for all sorts of reasons but let's let his performance speak for itself. He's a leader denied total leadership. He's on the edge of full blown meltdown and he trusts maybe only cassette tapes of his mother's voice. Bale is wired, no question and comparisons of his physicality and intonation with those of a certain Batman are inevitable. As much as I'd like to see Bale play the romantic lead in a piece of fluff (give the guy a reason to smile, for god's sake!), I do like the hard-as-nails, gruff, 'just-trying-to-get-through-the-day' worrier-warrior he excels at. I think it was competition with Matthew McConaughey on Reign Of Fire that started him on this physical-fit-to-burst road. At least our Christian doesn't whore stenches for Dolce and Gabbana.

And despite the marketing and Bale's clout, it's not really his movie even though he's the franchise guy. That honour belongs to a man who may go stratospheric next year once Cameron's Avatar is unleashed in December. He's a down to earth Aussie but he has been syringed into the Hollywood metasphere. Playing the mysterious Marcus Wright, Sam Worthington is the lifeblood of Salvation. He's the über-badman, a convicted death row murderer of the intro who signs his body over to medical science (fronted by none other than the eclectically talented Helena Bonham-Carter, a perfect example of an actress who defies typecasting. If I'd seen A Room With A View and had been asked to extrapolate her career into the future, the last set I'd have placed her on would have been Fight Club's). But I'm so glad I have an infinite capacity to be so bloody wrong. Why? Because the world, and Helena B-C, continue to surprise me. That's a good thing.

Reborn in the future, after his death by lethal injection, Marcus finds people to trust and help while the machines kidnap the dregs of the human race. His heroic stature comes a little too easily (that terribly annoying habit of Hollywood's, imbuing their heroes with superhuman abilities) but that criticism is soon tamed by a revelation that turns the movie around. It's kind of official as there are many shots that give away his secret in the exclusive Apple four minute extended trailer. It's a good reason he's strong and able to shrug off most physical threats. This is not such a guarded secret – most articles on the film have implied that there is more to Marcus Wright than meets the eye. It's how the film-makers riff on the idea of his otherness that is so satisfying. The Blade Runner line swirls into memory, "How can it not know what it is?"

Of course, due to this otherness he is ostracised but before his nature is revealed, he rescues the wonderfully named Moon Bloodgood. She sees a man with a strong heart to be trusted and risks seriously pissing off her friends and fellow soldiers in helping him escape. So the two stories running in parallel are: (1) The resistance resists while John Connor and the leadership (on board a submarine for added security) figure out their version of The Matrix's electro-magnetic pulse. It's not a great idea, a gizmo that just powers down the machines. It's too pat. An assault is planned but there are too many human prisoners for their deaths to be merely collateral damage so John rebels. (2) Marcus also goes into the heart of machine central to find out what was done to him and why. And there's lots of jaw dropping action and wonderful design work, naturally. To the film's credit, I saw it twice in three days and it stands up to a second viewing very well. No, I wasn't madly enthusiastic but I have a son who was and I enjoyed its detail in a more leisurely fashion second time around.

Again, depressingly, the only musical theme that punched through the multi-track smorgasbord of sound that calls itself a final mix these days was Brad Fiedel's metal smashing original "Dun dun... dun dun-dun!" It's a great disappointment to me these days to have to wait for a composer to actually put his or her mark on a movie. I cannot remember being aware of music in T4 (and purists may say that's a good thing). It really isn't. This was Danny Elfman. Where's the score? Was it lost in the mix with McG surreptitiously borrowing Spielberg's sound design for big scary machines, a very effective bass note which I suspect was a lot more complex than that? Elfman used to churn out wonderful melodies and themes. Hell, one of his cues from Beetlejuice was in an ad before T4 started. Crucially, his name was up there but the score wasn't, or drowned out by choices in the mix. Let film composers contribute something...

There are one or two silly niggles that the movie should never have allowed to become sores on an otherwise workable narrative. Skynet knows that Kyle Reese will become Connor's father and yet, their robots are looking for him not seeking to kill him. He's recognised a few times by robotic POV. Bang, shoot him, no John Connor... But then you underline the precarious silliness of time travel logic. The script should never have put Reese in that vulnerable situation. Secondly – and this is something that curiously didn't happen without consequence in T1 – if a robot arm makes punch-motion contact with a human body, that body is dead or as incapacitated without actually being dead. Again, you have to have the action (given) and you must strive to keep it credible. These Terminators only need to land one good punch and it really is all over.

But on the plus side, there is a sequence near the opening of the film that sees Connor escape from a trap, board a helicopter, fly off, crash and stagger out to be attacked by half an old style Terminator. And most of it is one shot, one extraordinary shot that must have taken months to work out, composite and render. Its throwaway nature, never calling attention to itself, is in direct contrast with Spielberg's Cruise and family drive off in War of the Worlds. As the virtual camera sweeps in and out of the car all I could think of was not "Gosh, I hope this lovely family gets away from the aliens..." but more of "OK, Steven. You have new toys. Could you refrain from showing me how great they are and just let me work up some sympathy?"

Two moments that I found oddly moving; the downed pilot cuddles up to Marcus and resting against his chest she hears his human heart beating. She says something like "I love that sound..." and then expertly timed in terms of camera movement and actors' performance, she moves back to where she was which Marcus misreads as closing in for a kiss. He moves his head down to accept it and then disengages just as fast as he realises she just wants the warmth. You really have to be looking out for it but it's very nicely done. The other moment is at the end when decisions are made and a human child holds a robotic hand and it's such a subtle movement (couldn't tell if it was an animatronic or CG – who can these days?) but it was oddly and literally touching.

One final thought.

I have an idea for a sketch in which the villain wins, has all the power in the world, a big desk and he's just sitting there in an office the size of a tennis court. He's the most powerful man alive. You just stay on him in all that space and slowly it dawns on you that, like Alexander weeping because he had no more worlds to conquer, the man is bored to tears. Careful what you wish for. Well, it struck me that if the machines win in John Connor's future, what then? In short, what is the point of victory for them? Can they feel the grass in between their toes? Can they love each other? Can they enjoy a pint of ice-cold milk after a three hour tennis match? What, in essence, are the machines fighting for? Worth a philosophical muse, that one. If you want credible action, solid acting, a narrative true to the series and a plot easy on the cerebral, then Terminator Salvation is right up your street.