Speaking of the series as a whole...
T1 was basically a survival-horror flick.
T2 was by far the best - I think you really got attached to little John and the reprogrammed Arnie-bot. There was a camaraderie there.
T3 was... forgettable. I think what I remember most was the inflata-boobs gag, and that's sad.
T4, for all that it talks about the human heart and tries to put some of that T2 feeling back, I think it misses. They could have done it. They almost did it. But it fell flat. You see the characters, and can recognize that they have certain feelings and motivations. But you don't feel it yourself.
It's certainly not a BAD movie. It's an action flick and fun to watch. Just not so immersive as I'd like. I think Elfman's soundtrack isn't quite there, either. There's a minute or two of Guns-n-Roses that fits perfectly, though.
