My favorite is definitely Tony Hawk 4, with 2 being a very close second. The character creator was a little more in depth, the levels were so much fun to skate around in, the soundtrack was perfect, the tricks were insane, and the best part: NO TIME LIMIT! I can't tell you how happy I was that I had an infinite amount of time to go and complete all the objectives on a level, even though they all had the standard 2 minute time limit. I think that out of the original four, Tony Hawk 4 perfected the skating game and remains to this day as one of my favorite games of all time.