There is a couple of great multiplayer-focused games on Xbox 360 (e.g. Dark Souls, Armored Core, etc.), but the eternal problem with such titles is that they are pretty much dead and less fun to play if there is no active online community playing it. This makes it difficult to decide whether is it still worth to jump in even if the game is already several months/years old.
Is there any service, public statistics or site that shows the activity of online gamers playing specific games on Xbox Live online (similar to PC-specific ways, like Xfire, GameRanger, or formerly GameSpy)? If not, what do you do to track health of online population for games you are insterested in?