I disagree. “Perfect,” as I understand the OP, is a more objective measure, especially given the contrast to “favorite” which is more subjective. A well written sentence is a well written sentence, no matter what your life experiences are when you stumble upon it. Fully realized and developed characters that you hate are still fully realized and developed. 30 superfluous pages that do nothing for the plot, setting, theme, or characters still need editing even if you really enjoyed reading them and would have gladly read another 30.
Your reaction to the book may change over time (and probably should), as may your ability to recognize or care about a book’s flaws. Whether the flaws exist doesn’t.
Excellent choice. I am using that criterion too – which ones have I held onto thinking I would actually read them again even with the big pile of unread ones. Besides the classics like Pride and Prejudice, I’d go with Geek Love.
I like Jingo, but for Pratchett’s finest novel qua novel I’d give the prize to Small Gods for its perfection of structure: it’s put together like a pocket watch.
That was going to be my other choice. Small Gods was the second Pterry book I read after Good Omens, and I still find time to re-read it at least once a year.