I'm coming more from the angle of card/board games, but I guess it could also apply to RPGs if you're the type who's interested in lots of
different game systems.
The potential of playing the game could be for any reason. Having enough players, length of play, learning curve for new players, etc.
BTW, if you're one of those fortunate people whose most-wanted game is also the game they'd most likely end up playing, congratulations.









