Xiaolin Showdown relies on its multiplayer to facilitate replay value. Unfortunately, this game doesn't have any. The monotonous and all-too-easy button-mashing combat is so been there, done that it's not even remotely interesting.
The presentation is passable, but the gameplay itself is an exercise in pure tedium. The pervasive sense of overwhelming boredom is what really kills it, since a competitive, group-oriented game should ideally be the exact opposite of digital Ambien.
Nobody ever really gets hurt in the game, no one ever gets knocked out permanently in these battles and there's no real indicator that your getting hurt, hurting someone else or accomplishing anything.