Pacman, Ms. Pacman and the one that gets played most often... Super Pacman. Coming in 4th, 5th and 6th would be Jr. Pacman, Donkey Kong and Donkey Kong Jr.
Edit: Looking at the times played count 7,8, 9, 10 (in order), go to Galaga, Kangaroo, Zoo Keeper, and Vs. Ice Climber.