Armstrong, Langford or Greb, depending on criteria. All three have serious cases for being BOAT even if one includes SRR or anyone else.
I don't rank Ali near an all time list, but I've seen good discussions about all time at Heavyweight. Greb was widely considered "P4P" in his day. Pep should get a mention high on the list. Hard to say really, my lists changed from day to day. Im a huge fan of Charles/Walcott/Moore but don't they they derserve the top spot. Armstrong maybe.
1. Robinson 2. Greb 3. Armstrong 4. Charles 5. Ali That's normally my set top 5 with Ali and Charles sometimes swapping. After that you have about 8-10 names that could rank in any order IMO. Likes of Willie Pep, Benny Leonard, Roberto Duran, Sugar Ray Leonard etc. I normally get killed for saying it and still think he's a great fighter, but Joe Louis is a bit overrated IMO. Definitely not the #1 heavy for me.
My top 10 without either; 2. Sam Langford 3. Harry Greb 4. Henry Armstrong 5. Ezzard Charles 6. Roberto Duran 7. Willie Pep 9. Benny Leonard 10. Mickey Walker