Gandalf wrote:
Chess has far more positions (as well as legal ways to reach them), and Go has even more.
As such, the AI behind them is less competetive (for lack of a better word) than that of checkers. This is even more true for the AI for a game of Go. Just think of how many combinations of pieces there are on any given move, for a 19x19 board for two players. It gets rather complicated. To date, the best Go AI (to my knowledge, please correct me if I'm wrong) has only the skill to beat low-dan pros.
EDIT: Link's broken in tags
http://en.wikipedia.org/wiki/Go_(board_game)