When people were doing athletes-of-the-century lists about 6 years ago, not only was he often the highest ranked boxer, he frequently made it into people's top 5 athletes overall.
I don't buy it. Here's what I can't get past: 5 losses.
When discussions on the subject occurred, I often got the feeling people were rating him so high for reasons other than boxing (i.e. social impact and being colorful). IMO those things shouldn't belong in the discussion.
(And if you do want to talk about Ali, the man, he was very flawed and hypocritical. I'm not sure why people try so hard to make a saint out of him.)
I have sympathy for his current condition but, I'm sorry, he just did too much losing to be considered the greatest. 5 losses? Come on. Marciano had none.