I hate to admit it but Mike Sigel was probably the best All Around player I've seen in my lifetime. Great at Straight Pool, a champion at 9-Ball, one of the best in One Pocket and played jam up Banks as well. The only players in the modern era who are in his league would be Efren naturally (an underdog to Mike at Straight Pool and Banks, a draw at 9-Ball and only a favorite at One Pocket), Buddy Hall who was Sigels' equal at 9-Ball, Banks and One Pocket but an underdog at Straight Pool and finally Steve Mizerak who was also Mike's equal at 9-Ball and One Pocket and a favorite at Straight Pool (the only one who was). Steve was not the Bank Pool player Mike was though.
Honorable mention goes to Nick Varner (strong at all games, but a slight underdog to Sigel in most), Allen Hopkins another great all around player and Jim Rempe who played all games top speed. The latter two didn't bank close to Nick and Mike's speed though. Jimmy Fusco was another great all around player, who did bank lights out.
In an earlier era, It had to be Ed Kelly who had no weaknesses at any game, Luther Lassiter who excelled at 9-Ball and Straight Pool (his One Pocket game was only average), and of course Harold Worst who had no perceptible weaknesses on any table, including Billiards. If you take his skill at Billiards into account, he may have been the best of all. There was no game he couldn't master if he practiced it awhile. He wanted badly to beat Ronnie at One Pocket and was learning that game quickly when he passed away. Worst was also a terrific snooker player as well, and perhaps the one American who could have gone to England and done something. He was that good!
It comes down to Worst in his era and Sigel in his, with Ed Kelly a very close third! If they had to play head to head at all games in their prime, I would bet all my money on Harold Worst. He only knew one thing and that was how to win. I sincerely believe he could raise his game to whatever level necessary to win. Harold was the "Efren" of his day! Mentally he was tougher than all the rest. I never saw him have a weak moment. I can't think of anyone else quite like him and that's why we still talk about him with reverence even today.