My least favorite wine question is "What is your favorite wine?" It's an honest and friendly question from someone that doesn't spend a lot of time thinking about the subject and I usually answer with a rambling mishmash of "Well, it depends a lot on the weather and the food I'm eating. Wines I love with beef in the winter are terrible with shellfish in the summer." At that point I can usually steer the conversation into something more fun, like pairing popcorn with Champagne.
My real, honest answer is more philosophical and more complicated, better suited to a one-on-one situation free of distractions rather than small talk at a noisy and crowded gathering.
Right now my absolute favorite wine is this 2009 Graf v. Schönborn Grauer Burgunder. What makes it so special? I haven't opened it yet. I have no idea how it tastes, and I'm not even going to review it for this post. Maybe in a week or two after it's had a chance to rest and I've figured out a good meal to go with it.
I've never had a German Pinot Gris before, and I'm intrigued to try the wine of a German aristocratic family that goes back to the 12th century. But a few years ago, my favorite wine was made from dandelions in central Ohio by very poor Amish farmers.
Simply put, my favorite wine is the next bottle, the next interesting grape, the next fascinating story. It's not that I don't appreciate all of the amazing wines I've tried in the past, and I've been let down by wines that I was very excited to try. But no wine will ever be as thrilling as that next mystery waiting to be sampled and studied and recorded.