You probably like a penis because of what it represents, and because you have one yourself. As far as being with a guy in your head not matching up to reality...oh, well. Sometimes fantasies are just fantasies.
Maybe you just like the thought of a man taking you as a woman because it puts you in a passive role. The penis is usually doing the penetrating, and putting the person being penetrated in the submissive position. Also, since you know how good it feels to have your *stuff* pleasured, it's probably easy to relate to how it might feel to give that pleasure to someone else with the same equipment.
I think you should just go for someone that you are sexually compatible with and who you love. There are a lot of GGs out there that feel more comfortable in the dominating position and doing the penetration. And, then, there are those that may not need anything to penetrate to make you feel like you are the one getting done. Then, there are tons of beautiful toys that can help you live any fantasy that you could possibly think of without having to put yourself in uncomfortable situations.
I tend to feel more comfortable in the dominant position. I do love women and have fantasies of women and their parts. Likewise, my SO feels more comfortable in a submissive role and he has fantasies that revolve around penises...but, like you, is not interested in men. When we both opened up to each other, we found that we were way more creative and fun than our initial fantasies. And, we also found that it's 2012...if you can think it, there's a toy for it. A lot of people aren't fan of certain toys, because they think it might not give pleasure to a woman. However, since it IS 2012, there are plenty of things designed for women that put them in the stereotypically dominant position that allow for her to actually feel her lover giving her pleasure. It's not like the toy would be giving her pleasure by itself...it requires someone else doing things to it for the woman to feel it. I won't link it here, but you can PM me if you really can't think of wth I am talking about.
So, I wouldn't write off men or women...I'd keep my options open. You never know what might happen, or who you might meet. My SO and I just found that we were really compatible in that particular department, and our openness allows for creativity that we have often said surpassed our initial fantasies.
So, though I love women...have fantasized about every part of them for years...my SO is way more entertaining and everything that she does makes her the sexiest woman alive IMO. I really doubt there is any GG that could drive me as wild...and, yeah, my SO doesn't have the same equipment as a GG but I've found it really doesn't matter. It's fun to NOT psychoanalyze your fantasies and just go with them. I really don't want to think about the deeper meaning of what turns me on, and I'm sure my SO really doesn't want to psychoanalyze himself either. So, just realize what gets you going and move on from there. It gets really boring when you just limit yourself and stay in one particular fantasy...there's a whole world out there. And, nothing is more fun than having someone that will just build up things mentally for you...so, you can actually be kind of in a fantasy when you are making fantasies a reality. The mind is a pretty powerful sexual organ, and so few people are willing to tap into how powerful things can be with the right imagination. But, that's just my experience and advice...take it for what you will. I just would keep my options open with all people and go for the person (relationship-wise) that does it for me in all ways. However, I'm as bi as the day is long, so my advice is always to keep your options open...so, again, take it for what you will. But, I wouldn't go for someone just for their body parts...it could be pretty hard to ignore the person attached to the penis, and they may have different feelings if they knew that was what really got you on board. It would be like a guy saying, "I really am attracted to men...but, I just love huge boobs...however, I am not sexually into women...I just like huge boobs...and, since I like huge boobs, I don't think I could ever be in a relationship with a man...I just need to sleep with a pair of huge boobs." Makes you feel sad for the person with the huge boobs that ends up with this person? Unless, the person with the huge boobs wants to be objectified for the night...which, there are people that do that. But...I don't know...seems kind of surface level lame a$$ sex. I can't just focus on one body part or action...but, I'm a little ADHD.
