I used to think that girls didn't like me because of my "geeky" interests - Star Wars, Transformers, LOTR, D&D, etc.
I didn't express myself and kept that secret, but then it was like I had no personality at all. I just tried to keep a low profile, fly under the radar because it was better than being teased, I just wanted to get through the day quietly, easily, painlessly.
In time, I looked back though, and realized that I don't think it was ever my interests that were the problem.
Instead, I think what WAS the problem, was a lot of things, but mainly it was my lack of a skilled interest of some kind, my lack of being good at something.
That's what I would say is the thing with "nerdy" interests. It's not the interests themselves that are the trouble, it's when they are your ONLY interests, and you don't have a balance of interests and topics to talk about. Also, it's important to clean up, stay in at least reasonable shape, either have or be working towards some kind of skilled career, and have some other skilled interest, an interest that you do and are good at, and gives you something to talk about that you actually do - so you're not just talking about the things you like, made by someone else.
We can't forget that we have to get someone into us, not into the things we like. I'm not trying to get a girl interested in Star Wars, or George Lucas - I'm trying to get them into ME. Guys in particular are expected to be good at things - especially if you're not naturally muscular and/or born to money. So we have to find a way to be someone, with a life, that another person could get into. I think if we can do all these things, it's possible to avoid the "nerdy" stereotype. I only wish I realized this 20ish years ago instead of today.
All in all I'd say that "nerdy" interests aren't necessarily a turn-off to girls, in and of themselves -
what DOES seem to be a turnoff, is ONLY being able to talk about "nerdy" interests, not having a variety of interests, not being good at any skilled activities, not having any thoughts of your own, and not being in a strong position in life. Again, I wish I understood that earlier, instead of just thinking I was "wrong" because I wasn't a "bro".