Ok are these the same Alians from the first game what happen to the blue squid robots they had a **** load of them and I think they were pretty bad ass. Don't get me wrong I love the alians in this one. Also why is there teck all red glowing. the ship in the first crysis was glowing blue. And what happen to the ice dome thing in the first game I thought that was there thing was climeitizeing earth. And (spoiler) in crysis 2 the consider nukeing the city when you think they would remember what happen in the first game when they did that. Sorry just fined it odd maybe those Alians were like the Russian and those ones are like the USA difrent races still love the game though good job.

They are the same aliens only that their technology has seen some changes and the aliens themselves evolved to adapt on a planet with gravity and hoter climate or it could be a compleat overhaul wich i doubt....

They're supposed to be the same race, scroll down a little bit to find the Crysis 2 section.
"The aliens in Crysis 2, which still relate to the aliens from the original games, have adapted along with the humans in order to dominate the intense warzones of Earth, going so far as to mimic their foes and commence an extreme overhaul of their technology."

http://crysis.wikia.com/wiki/Aliens

Damn, someone beat me to it, the link is still very informative though

Evolution Baby ... Kick Ass and chew bubble gum!