It's the same way with RPGs. Who cares if you found your perfect RPG, if you can't find anyone to play it with you?
I base this on absolutely nothing, but I'm not really convinced that "find a gaming group" is actually the predominant method by which people play D&D. And, if it is, I'm fairly certain that it's not a good thing that it is.
I mean, there's organized play for Monopoly, Scrabble, and poker (and that's good). But the popularity of those games isn't defined by an accessible "social network" of players: It's about people pulling out the Monopoly board and playing with their friends or family.
How do I find people to play D&D with? The same way I find people to play Arkham Horror with; or go to a baseball game with; or watch a movie with. I go to my existing friends and say, "Hey, you wanna play?"
One of the reasons I've really enjoyed our recent OD&D campaigns isn't really the ruleset: It's the megadungeon format that allows for every session to be a pick-up game while still being tied into a larger sense of continuity. Every time I meet somebody creative or geeky or just fun to be around, inviting them to the next OD&D game becomes an easy option.
Over the past year we've introduced about 16 people to D&D. And 6-8 of those people have stuck around and become regular or semi-regular players.
So I'll add that quality to the list of things a break-out game would need: A structure that makes it easy for new players to participate without instantly asking a huge, long-term time commitment from them. And I'll definitely be looking to develop similarly flexible formats in other RPG systems. I think Shadowrun has a lot of potential.
In my dreamworld, there would only be one unifying core system that everybody used. Such a system would need to be flexible enough to consolidate all forms of tabletop gaming, and yet strong enough to maintain a very high level of support in order to prevent gamers from scattering to the nine winds.
I hate to sound dismissive, but that's destined to remain a dream world. Because even if everyone ends up using the same game system, the flexibility you're talking about will still fracture the player base so that it's no longer a useful, unified social network.
This is another advantage D&D has: If I say "let's play D&D", you'll get a pretty firm idea of what type of game I'm asking you to play in. We will almost to the point of certainty be playing a small band of wandering heroes who fight monsters on a regular basis as part of our "doing good portfolio".
This is useful in three ways: First, it provides a clear set of expectations between GMs and players without any need for further communication. Second, it again answers the question "what am I supposed to be doing?" in a concrete fashion. Third, it allows for focused supplementary material which will be potentially useful to the vast majority of people playing the game.
There's already abundant evidence of what happens when this focus of purpose isn't present: Lots of games which have "the game is the game world" have found that supplementary material (the stuff you want to base your entire economic model on) is much more difficult to market. And you're talking about taking that basic problem and expanding it across multiple genres.
Furthermore, even if we conclude that we need a large social network for RPG players to plug into, let me point out that this doesn't necessitate a single, all-encompassing system. For example, FPS and RTS games both require strong social networks in order to support online play. But dozens of each type of game thrive at any given time.