Walter has the most TITLES. That doesn't make him "the best" automatically.
Ask just about anybody who has the best game, and they will say Weber. Ask Hardwick, ask Carter, ask just about any of the truly experienced bowlers, and they will say Weber. If it wasn't for his head, and his problems in the 90s, he would have easily surpassed everybody. When he is on (think last year's U.S. Open), he is unstoppable -- he does things nobody else can do.
Norm Duke is right up there today, but I don't think you can put him as the best ever.
Looking back, you've got to say Carter, then the original Weber. You'd do a great disservice to bowling history, too, to not consider Smith, Varipapa, Gengler, Marino, etc. Then a little later, you've got Anthony, Roth, and those guys...it would be difficult, in my mind, to call Williams the best ever.
Just my .02.