To be honest - disappointed. This is a rant post, if you don't like it then w/e. Just expressing my opinion. Crytek need to know where they've screwed up. Also - spoiler warning from here on.
So the best thing about the first game was the freedom. The amount of open space and truly destructible environments (trees could fall, the shacks could be blown to pieces) allowed you to approach situations in so many different ways. It was a joy to replay it over and over. Not only that, but the nanosuit was far better. Sure, it was a little bit more complicated, but it was so much smoother to use. Powers weren't mixed together, they were defined.
WHAT WERE THEY THINKING MAKING SPRINT A POWER

In Crysis 1, you could sprint in any power without it draining energy (and you'd run as fast as in Crysis 2). However, the one exception was using the speed power, which make you INSANELY fast, and ran your energy to zero pretty quickly. This was brilliant, because you could escape firefights in a blink. Really felt like you had an awesome suit on. But it's not in C2 cause if you used it, you'd probably of reached the other side of the level :/ Then there's the Strength power, ruined again. It was far better in Crysis 1 when you could choose this power. There was no delay in jumping and punching (as in C2 you have to hold the button down). What was possibly the most awesome thing about it in C1 was also that if you shot in power mode in ADS, it would drain your energy slightly as you would have zero recoil. Your strength counteracted the recoil, and that was great.
And I'm still not done... WHY DOES YOUR ENERGY DECREASE IN ARMOR MODE

This is another pointless addition. In C1 when you were in armor mode, which was the standard mode you'd be in if not in anything else, your energy would only decrease when shot/falling from great distances. This makes sense. In C2, it is constantly draining when on, and still when you get shot. This is because it's not the default power. Instead, your default power is NOTHING. That makes zero sense. Think about it - you would always want armor on from a defensive view so you wouldn't get shot from behind and killed unexpectedly. It's not a problem in C2, but it's still worse than before.
Fortunately stealth mode is pretty much the same. Shame the sprinting drains your energy though.
What else? Well they dumbed down the aliens in this game. In crysis 1, fighting aliens and humans was too totally different things. They were 'flying squid', so made for totally different firefights. In C2, they're just another skin for a human; 2 arms, 2 legs, a head and a gun. Woop-de-doo! What was wrong with being original? A ton of alien games already do the whole human re-skin thing.
Whatever, at least they put boss fights in the game. Oh wait...

So the boss fights are pretty much just normal enemies. There is not even one 'big' boss which you must defeat. They missed out on such epicness here. For example, imagine if something like this was going over the city and you had to jump building to building to blow it up: (also take note on the use of his powers in this video, THIS is how it should be done!)