My first choice is definitely Green Hill from Sonic 1 Genesis. Maybe it's not the most epic tune in the series, but it is a classic and also probably the first video-game music I ever memorized. Deciding which should be 2nd is the hard part. Assuming that the choice has to be a Stage music (not including the final bosses that have the main theme) I'll have to choose Rooftop Run Day from Unleashed. Rooftop Day is a fun stage and hearing the music makes me wanna run fast and pop some balloons!