<human>: Condense the text into a few key points

My SO and I are both freshmen in college. Our schedules this term are relatively light, so I had the idea of playing Pokemon White during some of my free time. My SO caught on and decided to play Black, and we joked about racing each other to see who can finish faster/better, etc.  This was a little over 2 weeks ago.
I didn't plan to play a lot, just something to do when I'm bored. He, on the other hand, has started to only play Pokemon. He even brought it to work. When he gets home, the first thing he does is open up Pokemon, and he sits in the same spot and plays for more than 6 hours in a row sometimes. When I ask him to stop playing when/wait for me so we can play together, he just snaps at me and makes some comment about having to win our race/finish quickly or something. Or if he's in a good mood, he'll say that he would stop at the next good stopping point in the game, but when I look over the next time, he's already kept playing. 
I've tried to talk to him about this affecting our relationship, he just says it's all in my head and that it's just a game, that I shouldn't worry about it, ending with some sort of promise that he'll play less and we'll spend more time together. But it hasn't happened.
He honestly barely looks at me anymore. When we go to eat, he brings the game so he can play instead of interact. When we do have a legitimate conversation, he would interrupt every few minutes with something like, "did you catch [insert Pokemon] yet?" or something Pokemon related.

Throwaway because this is so embarrassing. What have I done?

This has never happened before. How do I approach him about stopping without angering him/making him to want to play more to spite me, etc? Should I even be worrying about this? It just seems like we hardly interact anymore because he's always either on his computer looking up stats or staring at a DS screen.
<bot>: SO only plays pokemon in all of his free time, possibly taking a toll on our relationship. What should I do?