It honestly depends upon what you're looking for. There are a lot of different styled RPGs out there that appeal to a broad range of players. My game, for example, is more focused on exploration of the galaxy, but there are some that are focused primarily on combat and conquest storylines. Some are freeform where the players are the driving force, some rely heavily on the moderators to direct everything. It's all based upon what your interest are.
My game is always accepting new players (shameless plug).