To be blunt, I don't think anyone exactly enjoys hearing someone talk about games that they don't play and have no interest in playing. It's like if someone moved the topic of a conversation into, say, the time they landed a big trout while they were fly-fishing or a play they saw in a rugby match a few weeks ago. Unless you also fly-fish or watch rugby, the movement of the conversation doesn't leave you much to relate to, and depending on your proclivities that either a) makes you uncomfortable because you're suddenly un-moored in a conversation you may have felt comfortable to be a part of or b) makes you feel less than enamored of the person you're speaking to because they don't appear to have any genuine interest in relating to you so much as seeing you as a surface to bounce their own likes/dislikes/foibles against.
Gaming has become more mainstream, but it's not 100% there yet, and even people who play games of one genre aren't necessarily enthusiastic to talk about those of another.
If you want to "feel out" if someone shares your interests without alienating them, you might do well to compare your interests to things that are more likely to be embraced. If you said that the previews of Skyrim made you feel like you were part of one of the battles in the Lord of the Rings movies, for example, you'd be more likely to find some common ground- a hell of a lot of people saw those movies, enough that most people would be likely to admit to it. Heck, relating how Shepherd's relationship with the Council seems to parallel a real-life political situation might not even be the worst track.
Mostly, it's about being receptive- no matter what you're talking about, if other peoples' eyes seem to be glazing over, it's quite likely it's more about not feeling like they have a part to play in the conversation.