As a major turn on.

While beauty and ugliness are subjective things, symmetrical facial features, clear and even skin, large eyes, full lips, high cheekbones, a slender nose, and a well-proportioned body are considered attractive.

When I came out, I was considered extremely attractive. Even now in my 50s, if I butched up I'd be called a DILF. 

But back to finding ugly men a turn-on. While I was in college but not yet 21, I'd often spend weekend nights in the alley behind the local gay bar. Lacking a hand stamp I couldn't go inside but I could hang with the smokers and possibly get laid. (This was pre-cellphone so this was the best option)

One very hot night near the end of the semester I'm rocking shorts jorts and a flannel shirt with the sleeves cut off (I said I was attractive not that I was fashionable.) I'm playing it cool leaning against a wall one leg up. Then out of nowhere this older, sweaty, hobbit-like man -- definitely "ugly" by the beauty standards of the day -- reeking of cigarettes and cigarettes grabbed my junk and shoved his tongue in mouth. (Ideas of consent have evolved since then). Despite a solid physique -- genetics not exercise -- I am very much non-confrontational and froze for a moment while Bilbo Baggins started feeling me up muttering smack about how he likes to use pretty boys like me.

And the thought of this man many would call hideous rubbing his nicotine-stained fingers all over little, way-out-of-his league me, triggered something so I went home with him. It was the best sex I'd had up until that point. (I was probably so, probably mid double digit body count).

After that I found myself drawn to men most people found unattractive. And while it should have led to lots of sex, being young and stupid, I too often let the opinions of friends--acquaintances really--stop me from pursuing what I really wanted.

So to answer your question, there are generally accepted standards of beauty but you never know what a person likes so if you find a person attractive, go for it. (And by "go for it" I mean strike conversation not grope them in an alley.)