Halo 2 and GTA: San Andreas are still some of my currently most beloved games; but it's Paper Mario: The 1000-Year Door that's been in pole position for the last couple of days. The reason being that it's just THAT addictive. Its mix of RPG, adventure and platformer elements make it unique, not to speak of its nice graphics.
I even missed yesterday's champions league matchup real madrid - bayer leverkusen because of paper mario. if you're european and a football (=soccer) aficionade like me, you'll understand that it takes a lot to make me miss such a game. BTW I heard figp missed a penatly and the game ended tied, 1:1...