Even as Arnold Schwarzenegger was en route to becoming California's governor, the ending of Terminator 3 made it clear as daylight that another Terminator movie was unavoidable. As if written into the fundamental constructs of physics-- inevitably, possibly even without human intervention, the forces of nature would eventually bring about a Terminator movie set in the future where John Connor is a leader of the Resistance fighting the machines of Skynet.
And now, six years later (holy crap that was six years?), here's Terminator Salvation.
Notice how this one isn't called Terminator 4. This is appropriate, because it feels nothing like the other three movies. It shares little in common with them but the universe they're set in. Arnold isn't even in this one, believe it or not, except for a brief digital cameo.
Perhaps to establish some continuity with the old movies, they snuck "I'll be back" and "Come with me if you want to live" into the dialogue, timeless quotes from the old movies. But this time it wasn't profound or funny or anything. In fact every overt reference to the old movies was kind of disheartening, reminding me of how good those movies were and how far of a departure this one is.
To be fair, going off on a tangent was surely intentional. They wouldn't want to risk pounding the original formula into the ground and making a sad replica of a Terminator movie. This one is a straight-up action movie, guns blaring and sparks flying and eardrums splitting, and it makes no apologies.
Actually, judging it on it's own merits the movie is not bad, but gives no sense of greatness as the others did. This may have been an attempt at a series reboot-- in the vein of Batman Begins or Casino Royale-- where standard series conventions are thrown out the window and grittiness is increased off the charts. Except this series hadn't grown stale yet, and the old style was way better.
Terminator Salvation has one interesting parallel with X-Men Origins: Wolverine. In the X-Men series it was all about Wolverine's shady past, in Terminator it was all about the unseen future. Then suddenly we have these new movies that finally reveal everything we wanted to know-- but can we ever really be satisfied? It's like philosophy, which poses deep questions that have no real answers. Once the answers are within reach, the questions aren't nearly as profound.