Sir Mix-A-Lot -- Kim Kardashian's Ass Is Great ... But Baby Ain't Got The Best Back

Sir Mix-A-Lot likes big butts and he cannot lie, but when it comes to picking the best of them all -- the brother just can't deny the round thing that gets him sprung ... belongs to Jennifer Lopez.

Yes, Mix tells us he's been admiring Kim Kardashian's latest cake displays -- but still gives more weight to J.Lo's experienced bubble. In fact, he says her ass inspired him to write "Baby Got Back" ... after seeing it in all its Fly Girl glory on "In Living Color."

For now, Kim's gonna have to settle for a consolation prize from Mix ... who says J.Lo's 45-year-old ass still isn't ready to hand over the crown.

For the record Mix ... Kim actually IS 5'3".