Ganondorf is not great, but he's not bad enough that there isn't a single Ganondorf out there that will give you any trouble. The characters are balanced enough in this game that, unless you are the very top of competitive-level play (which no one in this thread is save for Nakat, Dabuz, and Nairo), there will always be a main of an arbitrary character X who will be better than you and own you, often even if character X isn't that good. Example, Shaya is a tournament-level Marth, but he lost to Tyrant's Captain Falcon in Brawl. Captain Falcon is awful in that game, but Tyrant knows Marth and is the better Brawl player.
So, I'd wager to say that if you haven't fought any Ganondorfs that have given you trouble, then you haven't fought a Ganondorf that's above your skill level yet and knows the Rosalina match-up better than you do. I don't claim to know what your skill level is, but this applies to all skill levels except the very top, which is what tier lists are ultimately decided on. When we're judging characters, as difficult as it is, we should try to see the potential of characters at the very top and judge based on options rather than matchup experiences (or at least we should try to come to conclusions about options from matchup experiences--what could we have done better here, or what could the Ganondorf have done better, and how would that have changed the results, etc.). I'm guilty of being biased based on my own mental blocks against certain characters (Jigglypuff) in determining matchup ratios, but I can admit that that's a bad idea and I try to be objective whenever I can, as I know that I'm not the best (yet) and people can use my characters and my opponent's characters at a level beyond what I'm currently fighting.
tl;dr: you probably haven't faced a good Ganondorf, he's not bad.
