I have always known DH and I are not 'soul mates' and we didn't fall in love over long conversations about shared interests. There was a very strong physical attraction and a mutual fascination as we are a bit ying and yang, although we share important values like thinking it's important to be a good person, valuing intelligence and not having any religious beliefs, for example. And we are approaching parenting in very similar ways. In many other ways we differ wildly: career, cultural interests, political views to some extent, etc. I have never developed any interests in the things that excite him and although he has tried over the years to sample some of my interests (with some success) he still defaults to his own preferences (why shouldn't he, after all?).
I knew even on our wedding day, that it could be a problem, but I also knew from previous relationships that you can have too much in common and get bored, and what's more the common interest can mask problems as you still have so much to talk about. As I value so highly the more important attributes e.g. He's hard working, loving, a great dad, a caring son, a loyal friend, and he loves me so much, I thought it would be ok. I still think it can be ok, but I am increasingly irritated by the fact that we struggle to have free flowing, stimulating conversations more than about once every few months.
I don't believe that your DH should necessarily be your best friend, but can it last when (apart from a common love of your DC) you get excited by different things?