Which is the most beautiful freshwater fish for you? Do you have it in your tank? If you don't would you like to get one?
As a kid I liked having tropical fish because they seemed to last longer than the regular goldfish.
I would probably have to say that it would be Discus, not by their shape or size, but by the vast coloration that they have. Sadly, I'm sure that tons of people agree and that is why the price for a single Discus is extremely high. I'd love to have a few inside of my aquarium, but they prefer slow moving waters that have a very tight specific pH range that isn't an option for me unless I were to monitor the levels on a day by day basis.
I also think that it can depend on just the overall pond or aquarium that they are in, since a black fish wouldn't pop out if it had black substrate, but if there was white substrate it would by far pop out anywhere it went.
I like the discus as well as some of the sleepers and gobies. Also a betta fan. I was at Petco the other day and they had a Halfmoon Plakat that really caught my eye:
Love that shade of blue.