I agree with this. I think LoL and WoW stand alone in their respective genres as the "big dog." They've been the most popular and the most polished games in their categories, and for a very long time. People are always expecting the next "WoW-killer" whenever a new MMO is released, but it never happens. Why? Because an MMO on release can not compare to the plethora of quality content in a long-established giant. Also, there's the effect of "all my friends are playing WoW," which, in a socially-based game that requires an immense amount of effort to reach a competitive level, will keep players tied to whatever their peers are playing.
However, both of these factors are a little less compelling in League's case. First off, League doesn't have an impressive amount of content for its age, IMO. There are many champions and a fair amount of items, but only a small pool of each are considered "worth playing" at a competitive level. If a competitor was able to release say, 40 characters that are all equally a viable (quite a feat, but possible,) then they'd be at about the same level of LoL in terms of diversity. But the more likely scenario would be a pool of 40 characters, out of which 5 are grossly overpowered (something that I don't think League suffers from... some champions are just "really really better"), and 15 are considered the "best."
Secondly, League doesn't require a great amount of dedication from each individual player in order for them to experience all the game has to offer. IP-grinding can be alleviated by purchasing RP. Since the game scales with you as you improve, and Summoner's Rift doesn't change, level grinding isn't a huge deal. It opens up ranked, but again, it's just the same song and dance in a more competitive setting.
So what is a player's motivation to choose League of Legends over other games? I'm not sure if community necessarily applies here. Due to the factors I mentioned above, a player's dedication to LoL can be a lot more volatile compared to what we see in MMOs. It's a lot easier to move from one game, where progress essentially exists in a 30-minute vacuum, to another that does the same thing.
I think the prime motivator is polish. Despite what people say, I think Riot does an excellent job paying attention to the players' opinions and observing the state of their game. Updates are very frequent, and we've seen many champions get completely retooled in the past couple of years. It's a neverending cycle, but they keep up with everything pretty darn well.
The biggest threat to League's success is not Riot making mistakes with champion balancing, but if they just stopped trying. Games like HotS with a variety of maps that make it seem feature-rich appear to be threatening, but I'm not sure i they'll knock Riot's crown off. I love alternate game modes, I mean hell, I pretty much JUST play ARAM. But I respect Riot's decision to focus solely on Summoner's Rift. That's the game. That's the way it's meant to be played. And that's where they want a huge chunk of players to queue. Modes like URF and One for All being permanent fixtures would just be a mess. Players would expect balancing and updates, and the team might not be able to provide them with the sort of polish that they expect from this company. Having half-assed features in a game greatly reduces its perceived quality. That's why the "lore gutting" is such an embarrassment that they'll need to rectify.
