A few points or tidbits to make since i've played Heroes of Newerth (the 3rd major game), Dota, and play Dota 2 now:
- Dota and Dota 2 are essentially the same game, although Dota 2 is missing a few heroes
- Original Dota is still gigantic in popularity, bigger than LoL, which is bigger than dota 2, followed by HoN which is quite small.
- HoN was supposed to be the sequel to Dota 1, until IceFrog had a falling out with S2 (the developers), leaving HoN with a bunch of 'classic' dota heroes mixed in with their own creations. HoN is a much faster paced version of Dota, with a lot more clicking and skill-shots and emphasis on individual skill than hero drafting (many of the new heroes are jack of all trades), and a number of annoying features removed (secret shop gone/start off with a courier: but you could argue they are more layers). I like it quite a bit still but noone plays it and everyone i know plays dota.
- Most hardcore gamers gripe with LoL (and now HoN) is the F2P/grinding system where payment or time is required to achieve a fair playing field. Dota gives complete access to the whole hero pool, which makes it the most balanced system for hero drafting easily. (HoN used to do the same but then switched to F2P)
- Second hand knowledge suggests that LoL has removed a number of features, archaic or not, like denying, pulling, runes, TPs, bottles, juking, mana management tactics, and has fewer items you have to activate (in the other 2 games your inventory could easily contain 6 activated items). LoL is considered the easiest to learn which is great, but I like the extra strategic/tactical layers that those features provide in HoN/Dota.
- Most sources also say that the consequences of dying or being out of position are much lower in LoL. Again, Dota is team fencing, and death can easily be the result of being out of position more than anything else. LoL seems to have a number of ways to make positioning less important including items which reduce the effectiveness of disables, and in HoN most heroes have escape abilities. The apparent result is that dying has the biggest consequence and is also the easiest to do in Dota, which drags your whole team down as the enemy gets gold and exp. The increased consequence of having new players on the team leads to more raging.
For me the ideal game would be dota with a few of the hon heroes i sorely miss like parasite, chipper, and engineer
[edit: article i linked is probably not worth it given its from 2011]