Definitely Ronaldo! He changed the game, he was the definition of a modern striker. Ronaldinho is one of the most skillful players ever but he was not as impactful as Ronaldo. Romario also is another great striker but Ronaldo was more powerful. Cafu was a very underrated player, very essential in Scudetto winning team at Roma and CL winning AC Milan.
Cafu underrated?! He's considered one of the best right backs of all times. According to me, the best RB of all times. The only player who's played in 3 consecutive WC finals, winning 2 gold medals and 1 silver medal. Any team he played for was considered very lucky to have such a fine player at their service.
Also Ronaldinho was a very impactful player. Once upon a time, he was the definition of Barca. But I know what you mean with Ronaldo. He had his own class.
It's funny how some of the best players of all times, gathered together at the same time period in one team. It's a dream to see a player like Roberto Carlos in a team today, let alone together with Cafu, Ronaldinho, Ronaldo, Rivaldo, etc. We have been so lucky to watch these players play in our life time.