I ask this because I just assumed that all the famous composers were extremely respected in their professions; however, from various piano teachers I have gotten the impression that some were by far better than others.

Also, please give a brief explanation of your ranking system.

its an art no matter how you look at it, composing that is, so its pointless to rate different composers best or worst, since its quite subjective. What you can rate though is individual works from different composers as best or worst, as all composers(artists) have their ups and downs and some works badly conceived could be a low-point in a composers life(some best works are also written in tough times in composers lives).

Having said that if you insist most bad to worse composers would come from the late 20th-21st century. Some of them are , with all due-respect in the "wrong business", if you know what i mean.

Someone has an axe to grind. My preferences run against music that sounds like a pile of instruments being attacked by a horde of rats, but there is so much 20th and 21st century music that sounds so much better than that. Have you done any composing? What's brought you to this forum? Why start off so argumentative? ... Or are you just trolling?

Schoenberg's pieces are something a little difficult to get used to.

I cannot point a bad classical/romantic/baroque/modern composer, but I can tell that I HATE comercial trash that plays over and over on the radio/TV, etc.

I'm afraid I just don't understand your question. Top 10 best, or top 10 worst? Top 10 famous best? Top 10 famous worst? None of it makes any sense to me.