It's difficult to say, actually. The three games are actually quite different in gameplay, features, and style. From what I've seen on the Internet, people seem pretty evenly split between Melee and Brawl. The tournament crowd much prefers Melee, no question there, but the more casual players (such as myself) could go either way. I guess it depends on what you want out of the game. Brawl is more simplified and random, so Melee would be better if you're more competitive. The two games have vastly different art styles as well.
There don't seem to be very many people who prefer the first. Although I prefer Melee, I still like the original Smash Brothers. Because of its smaller character roster, it is the most balanced of the three. I also think it has the best pacing, and the best stages too.
