Oscar De La Hoya Says Tyson Fury's Definitely NOT Best Heavyweight Ever

Tyson Fury, 2-time heavyweight champion of the world, undefeated (31-0-1) with wins over Deontay Wilder (twice) and Wladimir Klitschko ... the greatest heavyweight ever?!?

Hell no, according to Oscar De La Hoya ... who, standing with his girlfriend Holly Sonders, tells TMZ Sports the Gypsy King is certainly one of the greatest of this generation -- but not the best ever.

"Of all-time? All-time? So, you're disrespecting Muhammad Ali?" the former 6 weight class world champ fired back at our guy.

FYI, 6'3" Ali finished his legendary career with a 56-5 record ... with wins over George Foreman, Sonny Liston (twice), Joe Frazier (twice), and Ken Norton (twice).

For what it's worth, just minutes later, Ali's grandson, pro fighter Nico Ali Walsh told us Fury was a top 5 heavyweight ... and a bout between TF and his grandpa would be the greatest fight ever.

So, maybe not that crazy of a question.

Even if De La Hoya isn't ready to put Fury above Ali ... he still believes the trilogy fight was incredible.

"I thought it was a beautiful fight. I'm happy that Tyson and the Bronze Bomber gave us an amazing performance," Oscar said.

"I promoted the Bronze Bomber for 40 fights, and he always had a heart. So, I'm glad that they gave us a beautiful fight."