There may have been changes, but they where not for the better.
The story is the same... and i mean there is none, That was fine for 2006, but this is 2010! There should be at least SOME story. Now I will give the game credit, it looks AMAZING, and there is no slowdown, even when hundreds of aliens are swarming the screen.
Now on to the bad, The controles are the same, but they fell more slippery, like your charecter's on ice or something. The gameplay fells WAY more repetitve than it did in the old game, also money has been made scarcer so you'll have trouble properly "Arming up" before each level, Also it feels like they ratcheted up the difficulty, levels that I had little trouble with in the origional are now next to impossible. Also the blood has been toned down, dude, what's up with that?
SO overall this is not a terible game, but it seems like the developers spent all thheir time making the game look good, and not improving it.