I think Prototype has AMAZING gameplay. Whether you are punching a pedestrian or commanding an air strike... it's still great! There's a refreshing amount of blood and gore when you fight, but that's not what I bought the game for. I bought it for the abilities, particularly shapeshifting. This seems to be the first game I have played that features shapeshifting as the main power. I especially love disguising myself. That's one of my favorite aspects of the game! The sandbox aspect of the game is just the icing on the cake...
Graphics: Hey, they're not the best graphics around, but they're not EXTREMELY bad like everyone says. I, for one, am fine with the graphics. I don't understand why others hate it to the point where they render the game unplayable. The gameplay alone is enough to push this game past any visual flaws present on the surface.
Replayability: To rap this up, on a scale from 1 to 10, Prototype, in my opinion, deserves a solid 9.
Overall: One word... "AMAZING!"