It's no joke. It's the best Gamecube game possibly ever made. Especially as a launch title.
Nintendo is busting it out for a second time in the sequel to the smash hit series, Super Smash Bros. There's literally hundreds of unlockable content and a total of 25 Nintendo characters, each with their own moves and special attacks. There are three single-player modes (two at first), all unique and exciting to play.
Multiplayer is by far the hallmark of Smash Bros Melee. There's no annoying splitscreen at all, just free-for-all combat on a stage of your choosing (there's around 30 stages total). There are items as well, twisting the game in hundreds of different ways, opening up enourmous opportunity. Listen to the community about this game, as it is one of Nintendo's best by far. I bought a Gamecube just for this game. So get a Wii or a Gamecube and start meleeing each other to oblivion.