We like straight guys because we like guys, full stop. (Or 'period', as the Americans say
)
My secret theory is we like straight guys because we are irresistibly attracted to what we cannot have. We hope that, after a bit of drink, they might allow us to do things, or that one day they might 'discover their secret gayness' but they don't. They just remain straight.
On an external level, the present obsession with image and the metrosexuality thing, has made them even more body conscious (up to about 15 years ago, the province of the gay male). Which makes them doubly attractive and us doubly frustrated. ~X(
For what it's worth, that's my take on things.
But thanks for an interesting topic