Regardless of any and all opinions, Dota2 won't even come CLOSE to the subscriber/user base that LOL has established. In fact, all the other MOBA games COMBINED won't come close to WoW...er.. LOL.
And why is that? Accessibility and Game/Character Design.
NO ONE that hasn't played DOTA is going to have an EASY time getting used to DOTA 2. ESPECIALLY someone coming from LOL. First off, no camera lock. I understand DOTA didn't' have one but failing to implement this in DOTA 2 is just...well...it shows a complete lack of understanding of how to achieve genre success on the part of the DOTA2 devs. The lack of any real "tutorial" other than simply jumping in a bot game and feeding till you understand how to move the camera, use the courier, escape with tangos/quelling blade/or a skill/item, ect, really hurts as well. LOL literally holds your hand for your first few games and then encourages you to go test your skills against bots before you jump into a real game.
People ripped on WOW for its accessibility and ease of use, but that's what GETS non hardcore/legacy gamers INTO your game. I would wager less than 5% of people who HAVEN'T played DOTA1 or are coming from LOL will stick with DOTA2 simply because they won't even play more than 5-10 GAMES before they get frustrated/angry and just GIVE UP!
And the character design is another HUGE issue. While ALOT (read: most) of LOL's characters are blatant rip-offs, carbon copies, or simply are "inspired by" dota heroes, they are ALL (read: ALL) better designed, both in game, in lore, and in concept/name/title.
The MAIN reason I got into LOL originally instead of HoN or DOTA1 was the CHARACTERS. I looked at the entire rosters of all 3 games and LOL's champion list simply had better characters. Rather...these characters better appealed to ME. But clearly I'm not in the minority since this game has FAR more players than the others. I mean honestly, even the voice acting is better in LOL!
Don't get me wrong, I LIKE both games. There are some things about DOTA that I'm surprised haven't been implemented into LOL, but when it all comes down to it, I find LOL's champions, mechanics, and gamestyle more FUN (not saying BETTER) than the others. And by a significant margin.
TL : DR = Being Accessible and User Friendly is NOT a bad thing. LOL Champ/Hero Design > Dota's. Most popular does NOT mean best, but it means SOMETHING.