I don't see anything wrong with someone's favorite anime being SAO. We all have different tastes and interests. I could easily see it being a favorite for quite a few people. Just because there are a billion other anime shows out there doesn't mean someone has to choose one of the more "Trendy" or "Overly popular" categories. That's almost like succumbing to peer pressure. If you don't like it, that's fine; but don't think little of people who enjoy something you don't.