You're not of the exact same generation, so you don't share the same cultural references, but that isn't much of a problem. You grew up watching different TV shows and different movies, listening to different music and thinking about different political ideas. You were different ages when important events in history happened, so you have different references on the importance of various events -- and all these differences only serve to make your relationship more colorful.
You didn't grow up listening to the same music or watching the same shows, but you're not so far apart in age and influence that you don't know what the other is talking about. You have a grand time listening to each other reminisce about the good old days -- about all the things that were most important to you in growing up, all the things that meant something to you and why. You don't make each other feel silly for the things that meant something to you; instead, you see them as interesting, even educational. You don't come from such similar backgrounds, necessarily, but you're close enough to relate to each other, and that's the important thing.