Gold Miner & Lucky Letters are my favorites, but I play all of these games below regularly.

When the arcade contests were going on I was playing every other day or so, but am now playing about once a week:

3 point shootout
Acnos Energizer
Asteroids
Battleship
Chain Reaction
Classic Frogger
Dynomite
Elite Mahjong Full
Evil Care Bears
Extreme Football
gold miner 2
Gold Miner: Second Edition
Hexxagon
High Hat
Ice Breaker
Ice Hockey
Lord Cannonball
Lucky Letters
Mahjong Connect
Mahjong Solitare
Mine Sweeper
Pacman
Pinboliada
Pizzaboy
Scrabble Blast
Skee Ball
Snake
Solitaire Golf SLingo
Space Invaders
Sveny Excuse
Sweet Tooth
Ten Pin Bowling
Tetris
The Weakest Link
Yahtzee