Those free games arent very free >:
I'd say LoL is pretty balanced between free users and those who put money into their account. Games like Gunbound or Rakion (both free to play with the option of buying stuff) are severely slanted towards those who use cash, the gear/items you can only buy with cash give them a huge advantage over those who don't, it's practically impossible to ever beat them 1 on 1, regardless of how skilled you are.