Most reviews have been voted down to about 60% helpfulness. This is largly because of the game's unique mechanics. People who "get" them downvote negative reviews, and those who "don't get it" downvote the positive reviews.
I've been playing this game with many people starting with the demo around 2004-5, specifically in sumo mode. I have not played the campaign, as I rarely play without friends. I have played 1000s of matches, and learned how to play.
Jumping is hard for some people. If you're a hater, you'll probably hate this game and give up, but if you learn how to jump, you'll admire the jump mechanic. If you play against serious players who've rocked this game 100s of times, you'll have a blast. It's a fun balance of creativity, reflexes and strategy that never gets old.
This is a great party game. Hooked up to a TV with 4 wireless xbox controllers, this game was a staple at a burger night. Everybody played, and even new players had a blast. The quick game resets and no load times make restarts a snap. It's also fun to watch.
If you don't have a TV and wireless controllers, use a projector 4 keyboards, or game controllers - they're $10 on ebay, or mix and match.
It's old, but it's good. This game was created in 2004, so the textures are a bit low res. The controls may seem alien at first, but once you learn, you can use crazy combo wall jump moves and squish the competition.