Prototype is a good game but it has its flaws
Prototype is a sandbox game like GTA but dont expect to find it so beautifully done as GTA4, Prototype lacks that. Alot of buildings look the same and the models for the pedestrians looks the same Also they dont talk alot and they say almost the same phrases. The sideobjectives arent funny but are useful for get upgrades.
Now the upgrades, as you progress you will get points for make Mercer more powerful than before, think of it as a rpg element on Prototype, he can increase his health, add new combos and other stuff.
Prototype is quite distinguished because the gore of the game so if you like that then you must get it. Mercer has attacks that will cut on half humans, throw them at walls, well its quite violent. Also you will see the blood when Mercer consume a human or infected. Mercer can consume anything alive for get a disguise and be able to evade easily the military but the infected dont mind at all if you disguised or not and they will attack you.
Graphics are well... disappointing. The characters have almost always the same face expressions, the buildings, car and models look like old.
Voice acting is kind of, not bad but also not the best.
Prototype is a good game but also it has its flaws. The main storyline is fun and interesting but the sidemissions and that the game is like a GTA don't add alot of replay value. If you want a little more replay value you should get the consoles versions for achievements or trophies. Also if you hate the gore and all that then evade this game. You have been warned.