[…]if you’re male and your partner is female then I’m surprised that she has any interest in things like Thundercats or He-Man regardless of her age.

First, I wouldn’t suggest assuming that.

Second, the point isn’t that a partner has to like these things, but they do have to have some kind of awareness of them. You could substitute Smurfs, Family Ties, Michael Jackson’s breakout album Thriller, or watching the Challenger explode on live television because everyone in the school was watching Sally Ride go into space. Or George Bush’s famous “Read my lips: no new taxes” speech. There are a million events that are foundational to who you become. When the person that you’re dating–or in a relationship with–don’t share any of those cultural moments, it’s much more difficult to build a lasting relationship. Not impossible, but harder; that’s true with any cross-cultural relationship as well.

Common interests are nice, yeah, but they aren’t everything. Shared values—and values are very strongly shaped by the things you were exposed to growing up–are probably the single biggest thing; if you don’t share core belief systems (morals, ethics, what is important, meaning, etc.), then it’s unlikely that a relationship can survive.