As a straight guy, I like my arse because it works. Not too wide, so nothing falls out when I don't want it to, not too narrow, so it's not painful squeezing one out.
Can't go wrong when you have a normally functioning arse.
I've only ever seen the 'perfect' ass on a man once. I was in central London and a guy walked past with the tighest ass I'd ever seen, me and my friends were in sitting in a car and saw him walking from behind. We were all like
Then he met up with another man on a corner and kissed him.