Nope. The card game is based on a fantasy story of an ancient Egyptian pharaoh who, long ago, banished evil sorcerers and their magical "shadow" games played with real monsters from the world with the sevel Millennium Items.
It continues immediately thousands of years later when a youth named Yugi manages to solve the Millennium puzzle, which holds the soul of the pharaoh when the threat of evil returns. Together, they and their friends fight back the evil forces.
The comic strip (called "manga") and the cartoon (called "anime") teach valuable lessons in friendship, forgiveness, and warn against revenge, hate, anger, and meddling in magic and things beyond comprehension. In fact, Yugi and his friends make peace with many of their former enemies, some of them rather bloodthirsty and vicious, and turn them back to goodness and allies to help Yugi and the pharaoh's spirit in saving the world. Self-sacrifice is performed many times in order to save the life of another (and what isn't more Christian than that?), and it teaches than anyone who truly wishes to repent of their evil ways can be welcomed back (reconciliation with God anyone?).
True, there is "magic" (fantasy stuff; nothing real or anything like Wicca or other Neopagan) involved, but it is mainly the reason why evil returned. The pharaoh's spirit, although sharing the same body as Yugi, is benevolent and works together with Yugi. In a way, this is very much like the dual Nature of Jesus; equally Man and equally Divine, working together without any domination from any side.
Although it has some darker themes, the main theme is to end the magic that caused the evil in the first place. Magic is nevery used by the side of good; only through evil means, with a few exceptions. The valuable lessons, as explained earlier, could be used to teach kids how to overcome obsticles with their peers, and the moments of self-sacrifice and converting the once-enemies to good show true Christian values.
As such, I see nothing wrong with Yu-Gi-Oh!.