My parents used to dismiss or make us feel bad about our interest. I was determined to not do the same with my kids. It isn't the worst thing in the world to do, but it did strain our relationship during the teen years. When your interest are picked on, you learn to not talk about them anymore.

I don't give a crap about video games and think they are pretty pointless, but gaming is one of my oldest son's hobbies and I try to stay interested. I'll sit up in the game room and will watch him play, I have played with him, and I often ask him about the status of whatever game he is currently involved in. My younger son loves baseball. While I do like sports, I think baseball is the most boring one out there. I still watched the World Series with my son, listened to him drone on and on about why the Dodgers should have one, have caught balls for him while he practiced pitching, and cheer for him in the stands at his games. You don't have to love the hobby but try to show some interest in the things your kids love. I think that is the key to having a successful relationship when they are teenagers.

Edit: I appreciate all the responses and everyone telling me that I am such a good dad, but I am actually a mom. Glad to know I would make a good dad though!