Is all the fun gone from GTA 4?

Has all the fun been sucked out of GTA 4 by trying to make is so realistic, In San Andreas there was endless hours of fun flying jets and attack helicopters with missiles and tanks and slaying people by the bucket load, now all they have is just machine gun on a helicopter, also there are less activities e.g. demolition derby, driving schools and hidden bonuses, after you finished the main story line there is nothing to do