The 49ers legend -- who was widely considered the greatest ever during and after his NFL career -- says TB12's accomplishments are simply better than his.

Montana appeared on ESPN's "First Take" on Wednesday and was asked straight-up if Brady has replaced Joe as the NFL's G.O.A.T.

"Oh, I think Tom has taken his place on the top up there a long time ago," Joe said ... "So, he's had a tremendous career, he's fun to watch."

Joe said he's well aware of the G.O.A.T. debate -- "but if you look at what Tom's been able to accomplish in his time that he's played, I think it puts him definitely up there in the top of the list."

For the record, Montana's resume is pretty damn impressive -- 4 Super Bowl wins, 8 Pro Bowls, 2 NFL MVP awards.

But, Brady ... good lord.

7 Super Bowl championships, 10 Super Bowl appearances, 14 Pro Bowls, 3-time NFL MVP.

And, get this ... Montana's career passing yards -- 40,551.