i have played it for 2 years more or less, i think i was able to let it go like 3 months ago (when swtor was released, but now i also stopped playing swtor...so i can say im... free?)
havent played dota2, its the same genre.
LoL, for me, was a HUGE improvement over Original Dota in gameplay quality.
Nicer Graphics, better shop system, more balanced (in dota, when i was playing at least, mages damage didnt scale with anything but a weapon that increased most of the mage skills like 20%, thats it), clearer minimap (in dota those blue or purple dots were hard to see instead of the chracter icon in LoL)
for all those things i got addicted into LoL and not into Dota, i think dota 2 solved most of those issues, but LoL is still a great game
for me i think its LOL = Dota 2 > Dota 1
as i said didnt play dota 2, will try it for sure when its released, but playing LoL is so easy (i dont meaning in skills, but in things that make life easier) that makes me really like it