Before making the decision to invest your valuable time and money on a Facebook game, you might want to take a moment to stop and think, "Just how long is this game going to be around?"
If you've played a lot of Facebook games, you can often go with your gut. For instance, if it's made by Zynga, it will most likely have a longer shelf life than a game from a smaller company for several reasons: Zynga spends a buttload of money advertising its games and it has the most powerful weapon of all -- a loyal group of players who are willing, dying really, to try the company's next big game.
Inside Social Games has published an in-depth piece on how to predict a Facebook game's success that essentially boils down to this: If the game is still attracting new players after three months, it has got a chance in hell of sticking around.
Case in point: Kixeye's underrated Backyard Monsters. The tower defense game is not the most well-known game on Facebook, but in the context of the ISG formula, it's one game that might be worth playing if you're looking for something new to add to your social gaming repertoire.