Some people define best and favourite as the same... i.e. it's their favourite because it's the best in the series for them.
It does seem like a lot of people like older games more now then they did when they first played them. It could just be part of human nature. The thing about memory is that when you remember something the experience changes in your mind, in some cases making fond memories fonder.
Who knows... I don't think I'm old enough to be that nostalgic... Modern games may have spoiled me though.