It has to be Cristiano, he has been one of the best 2 players on the planet for over a decade and smashed all sorts of records. With R9 it is more what he could have been without that knee injury, he was unplayable on his day. But knee injury or not, i still don't think he would have went on to have the numbers Messi and C.Ronaldo have achieved as the other 2 have the attitude and dedication that is unmatched by anything ever seen before.
For me Ronaldinho had more natural skill and ability with a ball than all 3 of the above, but lacked the attitude needed to be a top pro for a sustained period of time.