I'm the biggest Lewis fan here, and probably the biggest downplayer of Marciano as well, but I agree with both things you said
No there are some huge Marciano detractors and haters on here. You are not even in the conversation of his top down players yet.
Marciano makes the top ten for me some days and some days not. He had a very short run at the top, very short and with a very limited breadth in variety of opponents. And any head-to-head consideration goes badly for him.
1. Muhammad Ali 2. Joe Louis 3. Larry Holmes 4. Lennox Lewis 5. Evander Holyfield 6. George Foreman 7. Joe Frazier 8. Rocky Marciano 9. Sonny Liston 10. Jack Johnson Next 10 (rough order): Mike Tyson, Jack Dempsey, Harry Wills, Sam Langford, Wladimir Klitschko, James Jeffries, Floyd Patterson, Jersey Joe Walcott, Gene Tunney, Ken Norton
Ali Louis Marciano Foreman Liston Lewis (sometimes I place him as high as 3 but not today) Tyson Frazier Holmes Wlad Honorable mention to the likes of Johnson Dempsey Jeffries Tunney I just don’t place that much importance on pre 30s fighters.
1. Joe Louis 2. Muhammad Ali 3. Jack Johnson 4. Larry Holmes 5. Rocky Marciano 6. Mike Tyson 7. Lennox Lewis 8. George Foreman 9. Joe Frazier 10. Evander Holyfield 11. Wladimir Klitschko 12. Jack Dempsey 13. Sonny Liston 14. Sam Langford 15. Ezzard Charles
Ali Louis Liston Foreman Lewis Holmes Tyson Holyfield Johnson Frazier (Yeah, I know... Liston is too high lol)
Lewis and Tyson above Holmes. No, not even close. But that's just me. I was asked by a nice person here to post this: 1) Muhammad Ali (Unbeatable in the 60s, was only beaten by great fighters in the early to mid 70s. No one could touch Ali in his first run as champion, and I personally believe he would have beaten every other on this list during that time.) 2) Joe Louis (do I really need to explain?) 3) Larry Holmes (Greatest heavyweight jab ever, and nearly as great a ring general as Ali...despite the cries of lack of competition he was unbeatable post-Norton to 1985) 4) George Foreman (just take in his entire career. Wasn't much of a boxer, but such a devastatingly heavy puncher with the added gift of being a truly terrifying finisher. Unbelievably enduring, resilient in the 90s. He had an outrageously great and heavy (but woefully underused) left jab. ..had he employed it a long with more head and foot movement he might have overtaken Holmes on this list) 5) Jack Johnson (An all arounder, like Louis. Possibly the most tragic casualty in boxing due to the politics of the time) 6) Jack Dempsey (Even moreso than Tyson and Frazier, the most id-fueled swarmer in heavyweight history. Very much like an unstoppable force of nature at his best, regardless of being so light for a heavyweight) 7) Joe Frazier (Greatest left hook and, when he beat Ali, probably better than Foreman and Dempsey ever were. He's ranked down because, like Tyson, he really didn't last that long at his peak.) 8) Rocky Marciano (I'm a bit grudging putting him over Lewis and Holyfield due to the rawther, uh...elderly nature of his competition. Hard to fight that record, though) 9) This content is protected 10) Lennox Lewis (his accomplishments speak for themselves imo)