Real easier, I think !
What really disappointed me after THPS 2 is the deletion of the "Big Drop". You remember ? When you fall from a high, you'll eat the ground. That was much more realistic, because in the next games, you can fall from the roof of an hotel and just land as if you've had fallen from a meter...
But the thing you've missed is, if you don't have Tony Hawk's Underground or higher, you can't know the "Fireman" game for two players. By making a trick, you can throw a fireball and smash your opponent !