If the highest level of pool players, such as: Corey, Shane, Alex, Mika, Ralf, Orcullo, Van Corteza, and the best Japanese and Taiwanese players, intensely learned, practiced, and played One Pocket as their main game for 10 years, how good would they get? - less than R.A. and Efren? - equal to them? - or maybe even better....but, unfortunately, we'll never know.
It depends on the individual player IMO, the game takes a certain patience and innovation that 9-ball lacks. So being a master in 9-ball will not automatically mean you will excel at 1-pocket.
That said, some of those guys show some of the elements that make a great 1-pocket player.
Alex was actually pretty good at the game in his younger years. I think he could have been great had he stuck with it. His style of 9-ball is the type of game that transfers to 1-pocket well.
http://www.youtube.com/watch?v=CrrBwmzVP3s
Corey with his innovation, knowledge of the rails, finesse and touch, he would have made a killer 1-pocket player. He could outthink, outshoot, and outmove people like crazy if he commited to the game.
Shane, he is going to play any game with a cue well but I don't think his natural talents would lead to 1-pocket being his best game. I think rotational pool is the perfect type of game for his strengths. I don't think Shane would be the best at 1-pocket in a world where everyone was playing it.
Mika, Lee Van, same as Shane IMO, their strengths that make them so deadly in rotational pool are not what makes a great 1-pocket player.
Orcullo, I think he might make a monster 1-pocket player. He has potting ability second to none and he really thinks through things well. IMO his strengths are not totally made for rotational pool, and yet he is phenomenal at it all the same.
Ralf, this is a tough call. I think he would be very good but I am not totally sure if he has the knowledge of the rails and innovation to be the best at 1-pocket. His style of 9-ball is control and making the game easy, 1-pocket is a game where you are constantly shooint from a tough leave by your opponent and control comes and goes quickly.
Wu and the other Taiwanese players? Wu, Kuo, Yang, these guys are in the same boat as Shane. But Chou, that guy might have been different.