My case would focus on the time between him beating George Gardiner in 1902, and losing the title to Jess Willard in 1915. Over that period he fights over fifty times, with his only losses being a questionable DQ loss to Jeanette, and a questionable decision loss to Hart. He is fighting a mixture of top contenders and lesser men, but he is fighting top contenders at every single point in this thirteen year time span. He basically defeats every significant heavyweight over this time frame, albeit the fights often don't happen when they should have. Before he holds the tile, he is even beating the top contenders multiple times, if they are game for it. I think that comparisons with Larry Holmes are appropriate, in terms of longevity and depth.
There is no case for Foreman if there is no case for Frazier. Beating Micheal Moorer doesn’t make you the GOAT like I’ve read here lol.
Dundee has his opinion, Steward, Miller, Futch… etc he can believe and say as he pleases, he was also friends with and cornered Foreman.
Louis Ali Foreman Holmes Frazier Lennox Mike Holyfield Dempsey Marciano perhaps not quite in that order, but something like this
Christ that’s terrible how tf do you get Larry, Holyfield, Tyson, Usyk and Wlad under a guy whose best wins are… a worn Frazier, Norton, Moorer, Lyle and Stewart? Maybe Old Cooney? - with one sided losses to Morrison, Young, Holyfield and Ali?