My partner

Actually Havingfunwithyou71 is technically correct in that you really can't pinpoint perfection. You can have your general preferences for sure, but different little details can appeal to equally.
My general preference is a lean muscular type body (think physique competitor vs a bulky bodybuilder) with decent sized, aesthetically pleasing cock and balls.
*that said, I have seen guys (and gals) from smoother, less muscular, all the way to competitive bodybuilders that I thought were just stunningly beautiful.