Only issue I'd bring up re Charles vs Spinks is that Spinks was unpredictable. Maybe he'd find a way to confuse Charles and out point him. Would have been a great fight that I think we can all agree on.
From 44 to 52 he lost two debatable split decisions to Ray and Walcott. Plus he was stopped by Walcott. But he beat both mean himself as well. His loss to Layne is reported to be an outright robbery. His losses to Valdes and Johnson were reportedly dull affairs that could have easily been a draw. His losses to Marciano, well that's Marciano. So I don't think the best version of Charles ever lost to a fighter inferior to Spinks.
Only Walcott and Marciano had a clean victory over him. Neither of those two are inferior fighter to Spinks imo. I'd favour both to knock Spinks out.
To be fair, prime(ish) Charles was between '46 and '51, in which time he has two losses. The fight with Violent Ray and Rubber match with Walcott. Ray's win over Charles is a complete robbery. Most who were there said Charles won clearly. And Walcott hit him with Boxing's equivalent of Thor's hammer. Charles ford have 4 official wins over both, and arguable 6 actual wins and only one loss.
Walcott and Marciano were not only ones to beat Charles. Clean victory or not (whatever that means), Layne, Ray, Bivins, Valdes, Johnson all hold wins over him too, as does Lloyd Marshall. If they can beat Charles, then Spinks is definitely in the hunt.
With another set of judges, Charles might also have lost some of the fights he won, so that argument cuts both ways. One of his wins over Moore was very close, for instance.
Just regarding the Ray fight, Oscar Fraley said something like "10 rows back Charles looked like the winner", but that closer up Ray was doing damage. He also said Charles was holding and retreating a lot, which wasn't going to do him any favours at the Garden in 1947. The AP had Charles ahead but only by a round, so I wouldn't really class that one as a robbery.
I wasn't really using the Moore fight against Charles, just making the point that this kind of argument is swings and roundabouts. Most fighters have a few close ones go for and against them over their careers. If close losses are to be asterisked, why not their close wins as well?
I've seen those, but I've also seen some of the papers (although the name escapes me) and I'm pretty sure they saw it similarly to the judge who had it for Charles. 8-2 ish, based on better boxing and sharper counter-punching.
There's a lot of excellent commentary here from both sides , I rank Charles as one of the greatest pound for pound fighters who ever lived, but when I think of great heavyweights his name just doesn't come to mind as quickly as the usual suspects.