If you think this game sounds interesting but are uncertain you should consider Infamous which is a PS3 exclusive. It is exactly the same type of game, a sandbox city with you controllling a guy with superpowers, deciding yourself if you want to use them for good or evil. Reviewers are consistently scoring it higher than Prototype too, saying that Infamous at least equals Protoypes good bits and has none of the bad ones. I haven't played Prototype myself so can't comment on the accuracy of that, but I recently played through Infamous twice just to get both endings, and I rarely bother to get to the end of a game even once these days.