Rally1000 is still my most played game for some reason
Text Twist a close second (word jumbles, insanely addictive)
Xrow a third (really hard variation on Tic Tac Toe)
Monsta! (except I finished it a long time ago)
Piloth which I play against my wife when we are waiting for the trailer to start at the movie theater (Othello)
The others I keep around but rarely play at all.