facebookUpdate: See the updated list for May, 2010. See 2011.

For the purposes of this list, I excluded any arcade-like, mmo, social trading, trivia, quiz, or voting games.

  1. Texas Hold’Em Poker (11,200,000) by Zynga. Number one game on Facebook, period.
  2. Word Challenge (3,800,000) by Playfish.
  3. Poker Palace (2,400,000) by Playdom.
  4. Scramble (1,100,000) by Zynga.
  5. Word Twist (810,000) by Zynga.
  6. Scrabble (586,000) by Electronic Arts.
  7. Lexulous (585,000) by the Agarwalla Bros.
  8. Blackjack (559,000) by Zynga.
  9. Scrabble (349,000) by Gamehouse.
  10. Bingo (244,000) by David, Davy, and Robbie.
  11. Twirl (205,000) by The Social Gaming Network.
  12. The Dot Game (183,000) by Player Axis.
  13. Wordscraper (183,000) by the Agarwalla Bros.
  14. Challenge Sudoku (150,000) by Zynga.
  15. Word Island (119,000) by Metrogames.
  16. Poker Texas Hold’em (83,000) by Gamedesire.
  17. Okey ve Tavla Oyna [Backgammon] (73,000) by 6Q.
  18. UNO (67,000) by Gamehouse.
  19. Chess (61,000) by Chess.com.
  20. Wordy (48,000) by 6Q.
  21. Poker (38,000) by Real Dice.
  22. Dice Challenge (36,000) by David, Davy, and Robbie.
  23. Zebra Mahjong (35,000) by MegaZebra.
  24. Mahjong II (35,000) by The Internet Content Network.
  25. Four in a Row (34,000) by The Internet Content Network.

Poker, word games, bingo, classic abstracts, UNO, and dice. Looks like there’s plenty of room for some more innovation and not a lot of competition here, folks.