Jackie Chan -- Bruce Lee Would Beat My Ass ... No Question

Bruce Lee vs. Jackie Chan ... it would've been more of a MAULING than a fight, so says Chan who tells TMZ Sports -- there's NO DOUBT Bruce was the superior fighter.

The two actually came face to face on the set of the '73 flick "Enter the Dragon" -- but that beatdown was scripted.

But when Chan hit the streets of Beverly Hills again Wednesday, he told us a real rumble would've gone exactly the same way.

There's more ... Chan also updates us with the status of "Rush Hour 4" ... and tells us that when it comes to doing his own stunts, he's toning it WAYYYYY down.

As Jackie put it, "I'm not young anymore."