I assume you mean SR3 considering 4 isn't out yet.
I really liked SR3 myself, but I feel it doesn't even compare to SR2 still. SR2 had the best balance of goofyness with enough to take it seriously, and it was the only one to compete with GTA with me. It had SO much to do, and they took most of it out in SR3, shrunk the map, made it less interesting, and made every character unlikeable.