Agree that you should talk about it when your dating. When dating, they will likely tell you they like it, but doesn't mean it is a priority. Seeing them prioritize most everything else over going to a game and going to games just to spend time with you is an indicator that they likely won't see the value in the future. Unless they really get into it and make it a priority, it probably won't last once you get married. There are many degrees of liking something. It isn't the end all be all, but not very fun to be blindsided with once you are married and your spouse no longer enjoys something you thought you could enjoy together.

My wife loves watching the games with me and doesn't like it when she can't watch them with me. She isn't fanatical like I am, but she really enjoys it and unless there is something important going on that takes precedence, she will watch with me. If she has another commitment, I typically delay watching via DVR and I think that helps maintain engagement/interest because it turns into something that brings us together instead of something that wedges us apart, something we both get excited about.