Writing a good novel

I was reading an interview with Jonathan Franzen this morning. In the article, he comments that commercially successful does not mean you are a good writer.
I have struggled with this very notion many times. The idea that you can write a book that is essentially unreadable by the general public, but it still be considered a "great novel" and then authors who are read by millions can be considered "bad" (poor Robert Jordan).
Isn't art individual? Meaning is it only good or bad based on the eye of the beholder?
I can't say, but I have read some of Franzen's work. I think it's good, but I don't think it's great. Then again, I can't tell a fine wine from a cheap one unless I look at the price tag.
Mark Twain said (and I paraphrase) that many novels were like a fine wine while his were like water. He then went on to say that everyone drinks water. Of course, I think we all consider Twain to have been a great novelist ho was also commercially successful.
An example - Louis Lamour. He wrote westerns. They weren't great writing. They sold millions and millions of copies and to a certain audience, they are great. He reached people. He had a rabid a loyal following. People were sad when he was gone. I think this constitutes a great novelist. Was he the next J.D. Salinger? Obviously not, but he probably didn't want to be.
I hear elitist artists often lampoon commercially successful writing as "bad". Then again, at one point those same elitists tried to gain acceptance for publication.
I don't know what the answer is. I personally think judging a work as good or bad is in the eye of the beholder. Some people maintain, however, that they can tell good writing from bad (and we exclude the truly bad stuff...those that are made of poor grammar, cliches or stereotypes - there are basic rules).
I suppose I would like to be considered a "good" writer. Since I don't think anyone can give me that label other than readers and (hopefully) fans, then I suppose I will be relegated to the same "bad" column as writers like Terry Brooks and Robert Jordan.
I should be so lucky.