Larkham was better than all of them in my opinion. The bloke just glided through gaps or threw magic passes to put blokes away. All with the luxury of time to do it, or so it seemed. True champions always look like they have time. JW was effective in his day, but once the Dad's Army pack retired, he began to get injured, because he could not hide in the pocket and kick drop goals. He had to stand in the line and attempt to get a backline moving. He failed to do this. Larkham did it behind a pack that at best, held its own, but certainly did not dominate like the Pommy 03 pack did. And one other thing Larkham had to deal with that no other 10 had too, was Gregan was his 9. Imagine how much better Larkham would've looked again had he had a 9 who could actually pass it to him!
As for ROG, please? Granted, not many teams win matches when they enter into a kicking duel against him, but he is an absolute liability in defence. And at test level, again in my opinion, that discounts him immediately. Players like Darcy, O'Driscoll, and the fullback (name escapes me sorry), would be legends of the game had they had Larkham inside them.