League of Legends takes the crown.
Only because it's way more accesible and fun even for completely new MOBA gamers.
Dota 2 will most likely pull the HoN crowd towards it, being more elitist and competitive game. However the pace new heroes/patches come to LoL and considering the new game mode that might revolutionize MOBA, I don't except to see/hear much from Valve's version :J
Oh yeah, LoL has always loads of gamers, even during low hours. I'd like to see a B2P game do that :>

