Any doubt I had about Efren being the best ever were erased at the 2004 DCC, when I lost a C-note on Shannon Daulton in a tournement bank pool match against Efren. Efren played some of the best bank pool I've ever seen. I firmly believe that Efren can master any cue game he chooses to the point of being clearly the best (excluding 9Ball, which, like Billy stated, is almost a breaking contest at the top level). From conversations with a friend who has known Efren for years, it is pretty clear that Efren doesn't have the type of ego to play a particular game (e.g. 14.1) just to be the best at it. His thing is to provide for his extended family in the P.I., play as much chess as he can, and try to keep pool in perspective. Remember the scene in The Hustler where Eddie beats the guy at 3-cushion billiards even though he'd never played before? I can picture Efren doing the same thing to champions in snooker or 3-cushion or banks or whatever. Put enough money on the line and he would learn all the moves pronto. and proceed to outsmart and outplay the other guy. He's a true one-of-a-kind whose level of skills we may never see again.
