Cuba Gooding, Jr. -- MOCKS PRINCE FIELDER'S NUDE PIC ... 'Looks Like 2 Midgets In An Arm Wrestling Contest'

Prince Fielder KNEW people were gonna have a strong opinion when he stripped down butt-naked and posed for the ESPN "Body" issue ... and now, Cuba Gooding Jr. has delivered.

Cuba -- who just revealed he's got a role in Ben Stiller's new show "Big Time In Hollywood, FL" -- took his first peek at the nude Texas Rangers big man while in L.A. yesterday.

He laughed ... he joked ... he compared Prince's physique to "two midgets."

It's pretty funny. Think Prince is laughing, too?