I regard Ronaldo as an excellent player, in spite of that I don't think he's as much of a match-winner that Ronaldinho once was. I could've seen that yesterday. When Portugal needed him to lift the team and do something out of ordinary to keep them in the tournament, he kept popping the ball at the keeper or losing the plot in his dribblings, he has done very little to contribute even though people say that he's on top of his form (which, I think, is not the case at the moment and hasn't been since March or April).
In a situation like that, Ronaldinho scored a brace against Chelsea in the Champions League. They did end up losing the game 4-2 and out of the competition, but they got close to qualifying only because he was there to give them that spark of hope. The same goes for a CL semi-final a year after, when Barcelona couldn't break Milan and he turned up with a sublime pass to Giuly, with Gattuso on his back.
Then there's that game at Bernabeu, when he absolutely humiliated Real, scoring two goals. He even got a standing ovation there, which wasn't the case for Barcelona players for 20 years.
Ronaldo comes handy when we play against weaker teams, he usually destroys them on his own. I think he's yet to produce a sort of magificent performance against a very good team in a crucial moment, i.e. when United are down by a goal and chasing the result etc. A sort of performance that would make me wonder 'How the hell did he do that?'.