Hey, I still play Smash 64! I play all of the games.
However, I play Melee and Brawl more than 64 (my friends don't quite like it as much. Probably something to do with the lack of airdodging or the general slowness of the game. I just like the ridiculous comboing that happens, the importance each move made has, and Ness being top tier), and Melee more than Brawl. Well, I might play Brawl more than Melee, but I enjoy Melee more than Brawl and when with my teammate, we play Melee much more and enjoy it a whole lot more. However, some people complain that it's not beginner friendly.
While that is entirely true, this is why Melee is more competitive. It's harder and it makes you use your brain. Brawl does not demand as much from the mind. That is fact.
So, I guess that's why I like Melee more. It makes me think and gets me more involved. And when I'm more involved I just enjoy the game more.