Personally I like the games in the following order:
Super Smash Bros. (N64), Super Smash Bros. Brawl wii, Super Smash Bros. Melee gc.
There was just something that seems a little bit off with Melee. Sure it is fine for some casual fun, but it is certainly not the best in the series. I still recommend playing it though if only to see how the series has progressed.