Here's my opinion about Prototype 2. Really really like it. Click for details!
In the first time I played this game, it's little interesting. With new story and gameplay. After sometime (in the first 4 hours), I think I may get dissapointed because it's just following the Prototype's gameplay. For example, with the same enemy, like Brawlers or Super Soldier (ORION), or same weapon (in that time I just unlocked 3). But after playing it again for another mission, I find it was addictive. You will find that another story is prepared for you. It's really have element of surprise. I didn't expected those things, and really want to know the game until I defeated the game.
Another good-differences that Prototype 2 has is the better graphics. Different Blackwatch soldier uniform (I like this version more than the previous one), more detailed in Heller's weapon, and Cities' graphics. Although it will be need much more hardware qualities, but it's worth it.
About the control, Heller is quite easy to be controlled. Ordinary moving with W-A-S-D, also with special sprint, super jump, airdash, and hovering. But is it only me that think that Mercer's is easier to control? Especially in hovering and airdash. Don't know about that, but I think it's doesn't really important.
Conclusion: Surprisingly good (It had element of surprise, really!), rate it: 7.5