Wally Lewis is the best I've seen. Period. At Origin level there will NEVER be someone who can dominate for such a long time in the one position again. That said, it would have been interesting to see how he would have gone week in, week out in the NSWRL comp had he been down there for a long time earlier in his career. The King supposedly wasn't the best of trainers so who knows what may have happened if he had gone down south. That said, I'd put money on him being a success anywhere in any era!
As far as club players, you couldn't get better clubmen than Langer, Terry Lamb or Kevin Hastings but as far as the best I've seen - here's my list from 1980 on.
Backs.
Lewis followed by the likes of Johns, Lockyer, Sterling, Kenny, Langer, Daley, Fittler, Meninga, Belcher and to a lesser extent Stuart, Ettinghausen, Michael O'Connor, Eric Grothe, Dale Shearer (if he wasn't so injury prone he would have played a lot more than 20-odd and a dozen test matches and was naturally brilliant!)
Forwards.
Lazarus, Steve Walters, Webcke, Roach, Clyde, Pearce, Ray Price, Harrigan.
Lot of NSW players in there huh? I'm a QLDer but those buggers certainly have had some talent to draw on!