Well, I just completed Prototype and I must say that it was a little disappointing to say the least.
The storyline was pretty good, but somewhat inconsistent and I ended up wondering what happened to certain key npc's.
But all around, Prototype is fun sandbox where you can destroy virtually everything and get away with it. After completing it I got the option to start a new game, with all my stats at my current level. This is good because I can just go on playing until I don't want to anymore.
Fun gameplay and fun killing everything. The game is hard! I finished it on Normal, and that was a real struggle. I don't even want to know how Hard mode is.
I did enjoy the game, but I found the infected creeps to be annoying and I really wish it was a way to eradicate them all and go insane without them ruining it for me.
These are my thoughts on Prototype so please don't take my words to seriously, who knows, maybe you will enjoy the game more than me.

Enjoy playing the game and have fun

"Live every day like it your last, who knows, it might just be."