To be honest I've always considered Link the main guy in Super Smash Brothers from the beginning, though that may be because Zelda was always my favourite. But still I would love the game with Mario, Luigi, Bowser, Yoshi and Peach in it or not. But that's not really the debate, that just came up somewhere so I thought I'd say it.
When I was younger my favourite game was definitely the original Super Smash Brothers and I remember my excitement the very first time I got my own copy of the game, because it was just everything I looked for in a game. A few years later Melee was released, and as soon as I started playing I was amazed. At that point the thing that probably drew me in was the many characters to choose from, as opposed to the 12 or whatever from the original. At the time I remember me and my friends sitting up for hours just playing every combination of character, stage and items for a long long time. It just felt like the most amazing game ever created because it was such a huge step up from the original, and even though this isn't about the other games in the series it still matters to me here. I've never had a Gamecube myself, but me and my friends still bring this game out from time to time not for nostalgia, but because I think it's just as great as any game made today.
Grand Theft Auto III... I don't remember it that well, but I remember playing it a few times, and though it was fun and was a huge step up for GTA as a whole, it just didn't provide the entertainment factor everyone loves from SSB. Though people don't really think about GTA III these days and most of the time it is buried behind Vice City, San Andreas and IV, Melee is still worth playing even with Brawl out. As for something like graphics, SSB was supposed to be cartoony, and I don't think anybody expects them to be any better. It's supposed to be fun, and that's what games are all about. In this case I just have to say SSB is the more fun game. So, vote one of the most entertaining multiplayer games ever in Super Smash Brothers Melee. It's the righht choice.
And I'm even part of the nWZo.