There's not really any such thing as an active OnRPG community in any one game...at most you'd be able to find 1-2 OnRPGers playing the same game.
I'd suggest checking out what ppl are posting in the screenshot thread and hop on board? There's people playing Battle of Immortals (but the CB is ending soon I think), people playing WoW, and of course Buttons who has been playing FFXI for like the last 4 years.