Crysis
These aliens lived in a zero g environment and fought in many different robotic vehicles, with the main one being the flying one with tentacles. In addition, their main ability was to make the surrounding environment uninhabitable by freezing everything solid(You could survive because of your nanosuit). Not to mention all their vehicles were unique.
Meanwhile....crysis2...(These are supposed to be the same guys.....)
Only special power they got is they are able to release a spore virus that can infect and kill humans(This wasn't in the first game either). Literally the only similarity is that they are both based underground. The only vehicle they get is......a chicken tank walker thingy?
They also left the crysis1 cliffhanger unexplained. Aliens are ******** now and it might as well be a different game. Lastly, at the end of crysis you see hordes of seph pouring out across the world, simply not ever mentioned either. ****ed this entire game's story up, just to accomodate consoles. I LOVED the alien design in crysis 1 and their weaponry.
Then there's the final boss fight in both games. Crysis one your fighting the giant alien warship. Crysis 2? 4 cloaked guys that, on the hardest difficulty, let me sneak up and kill 2 of them with stealth kills, then the other two were just a matter of pressing Q to holding left click. Such fail.
/Rant. Don't think I'll be getting Crysis 3 if its made; they completely ruined it for me.