For me, it's his all-too-slick, pretty-boy cockiness that I don't like, and I think that goes for many. His football is amazing, though. Let's be honest...Messi is easier to like.
See I don't understand that. Messi and his father were prosecuted for tax evasion just recently and convicted of it if I am not mistaken, but he is in your eyes easier to like? While Ronaldo might seem arrogant, or all-too-slick in your words, the truth is he donates his blood at least twice a year (doesn't even want to get any tattoos because of it), was a bone marrow donor and is known for supporting children's charities. From what I can remember Ronaldo has always played for his country and according to his teammate Soares Ronaldo was an inspiration for all of them in yesterday's final even on the sidelines and in the locker room in the halftime, always encouraging them and believing in them. It takes a special skill to make a team better. Ronaldo does it with Portugal all the time, but I don't get the feeling it is the same with Messi and Argentina.
Frankly I think that Messi is as arrogant as they come, but hides it better perhaps that Ronaldo.