Yes? No? Kinda?
There are a lot of guys here who'll say, "I have ZERO interest in straight guys. Too much effort."
Then you have the exact opposite, "You always want what you can't have...." and "Forbidden fruit tastes so much sweeter...", which is two-fold.
1) The challenge.
"I just LOVE the chase." "Do I have enough game/hot enough/clever enough/etc. to bag even a straight guy?" "I can manipulate anyone to do whatever I want. Watch!" Similarly, "I think everyone is at least a little 'bi' deep down, and I can prove it." Etc.
2) The safety.
Some gay guys chase after what they can't have, specifically because they know that they can't have it. That is, it's not the challenge aspect of it, it's the safety aspect of it. "I don't have to worry about it ever happening." Or, "In the odd event that it does happen, it'll be a one-time thing." I could list thousands of reasons for this; fear of a commitment/relationship, discomfort with sexuality, etc. Some also think that if it DOES happen, that straight guys are safer than being with another gay guy (in respect to STDs). This misinformed thought is typically based on the idea that gay men have more partners on average than straight men. The biggest aspect of the misinformation is that numbers aside, sexual contact with just about anyone, carries a potential risk factor.
Yet another aspect of this, is that some guys feel that they can actually be "themselves", when there's nothing to prove. Just like a straight guy hanging with a straight friend, in a non-competitive, non-threatening setting, they just hang. A straight guy hanging with a woman, acts differently if there's the slightest potential between them. Sometimes a gay guy will feel more at ease hanging with a straight friend where there's no potential, because there's no need for the posturing.
I shouldn't flushed this out better, but these are just some quick observations.
Now, if someone could explain the opposite to me, how straight, and often married, men seem drawn to me like I was an over-powered electromagnet.