Add Sly Stallone to the list of people who thought Mayweather vs. McGregor was a farce ... with Rocky himself telling us he's over the hype and moving on to the "REAL" fight -- GGG vs Canelo.

We got Cobra (watch it, it's a forgotten classic) leaving the Palm Beverly Hills and asked if he thought the GGG/Canelo fight would be more interesting than Floyd and Conor.

Stallone didn't hold back (just like he didn't in "Over The Top," another freakin' gem from his resume) and told our guy it was obvious which bout would be better, cause only one is legit.

Listen to this guy ... he was able to clear his name after being framed in "Tango & Cash" ... (buddy cop staple on a "Lethal Weapon" level, just trust us).