I am going to throw a nomination out for World Poker Tour. The AI is pretty good...it will actually bluff and fold better than the other games I've tried.
The top feature for me in this game is the offline custom tournaments. The single player mode features a career mode where you play in different levels of Hold'Em tournaments and try to win your way to the next skill level. The custom tourneys allow you to set up to 200 player tournaments featuring any kind of poker you can think of, along with all the classic wild card choices if you want. You can choose the buy-in amount (which coupled with the amount of players dictates the tourney payouts) as well as the AI skill level.
Online is pretty much as good as the people who are logged in playing, pretty much like any other poker game I guess. There are some affiliated online tournaments you can sign up for ahead of time as well.
Its really good stuff. I have set up 200 player 5 card draw tournies with 3s and 9s wild along with straight Omaha tournaments. You can find this game for $20 or less used, if you like console poker games this is a must-have.