I like my bikes that have compact frames, because they do what I want. I think that makes them look good.
I like my bikes with horizontal top tubes because they do something that I want, so that makes them look good too.
I like my antique curved bar (cantilever) Schwinn frames. I like my ladies frame beater bike. I like the frame on the 39 year old trike too. It works.
I buy a bike depending on what the bike was designed to do and how well it does it, who cares where the top tube is unless there is some kind of a problem like clearance? I like a sloping tube on an mtb for the clearance.
But I never notice a problem or even a difference when riding my mtb with a horizontal top tube compared to the one with a sloping top tube. I never even though about it until now. I love both bikes, don't make me pick one or the other, that's silly.