Bale produced a stunning all-round display and two goals to almost single-handedly shoot down Scotland on Friday night.
Coleman said: “In this country we talk about the great John Charles, Ryan Giggs, Ian Rush. Southall was the best goalkeeper in the world.
“But there’s no doubt in my mind he will be up there with those guys.
“He’s only 23. It’s not a case of ‘can he be up there with those guys?’ He will be.
“I have not seen many better performances by a Wales player than that — and that’s apart from his two goals. As a manager you admire players from afar and you know someone is a good player but it is not until you work with them when you find out exactly how good they are.
“I knew he was good but against Scotland he was a different class. The goals capped off a brilliant performance.”