I think the formula for being the king of a multiplayer oriented thinkers' game genre is a positive feedback loop between a large casual community and a respectable competitive scene. The competitive scene provides the game with a reputation of being well designed, well balanced and deep enough to withstand years of exploration by hundreds of smart people and still remain an interesting test of wits to them. The large casual community provides the critical mass of potential high level competitors and makes up most of the actual playerbase.
This is why chess was the king of board games until computers beat the champion. The main selling point was not "The queen can move both straight and diagonally, awesome!", "The board has stunning graphics!" or "The story is amazing!". The main selling point was the champions, chess was the game smart people play. At the same time anyone could quickly learn how each piece moves and start playing. If you wanted a nice battle of wits with a friend "the game smart people play" was an accessible option for you too.
This is why Starcraft is the king of RTS. It doesn't matter if another RTS game is better or not. Even if Starcraft is not the best RTS game it is still the game professional strategy gamers play and it would take another game many years to build up a competitive scene capable of challenging that title. At the same time anyone can play "the pro strategy game" through the story, play against the AI and against friends. That is why they put so much effort into the story of a competitive online game, the story is how casual players explore the game at a comfortable pace.
This is why League of Legends is the biggest MOBA. Riot puts a lot of effort into making the competitive scene look good with presence at events, prize pools and marketing to make it the MOBA for pros. At the same time compared to the rest of the genre the game is oversimplified, shallow, has a slightly less hostile reception for new players and more options for practicing. It's designed to be "the MOBA for noobs" but still stays respectable and appealing as long as they can keep up the image of being "the MOBA for pros".
Edited by Kuggen, 12 May 2012 - 10:03 AM.