Radical Entertainment’s rather impressive looking sequel to Prototype is no longer a vague “2012″ title, as Activision stamps out a firm April 24th date during Comic-Con. Prototype 2 will hit PS3/360/PC next spring, pitting new infected hero Sgt. James Heller against the military, various mutated freaks, and the first game’s Alex Mercer. Tags: GameTrailers.com,…