Yu-Gi-Oh! is a pretty decent game. A lot like Magic: The Gathering, except heavily simplified. But unlike most Magic knockoffs, it clearly had some real thought put into its design and rules, so it still holds its own... at least, it would if it hadn't gone the unfortunately common lameass route of creating increasingly powerful monsters with no drawbacks, effectively making decks age quickly and become severely underpowered and useless in modern play. A shame, really, because it was a good bit of fun before they got greedy. Kinda surprising that Pokémon hasn't done that same exact thing.
P.S. Thanks