I think how you vote has a lot to do with what your romantic ideal is. This is how I think the four choices can be categorized:
Angel--Written in the stars. Angel and Buffy were dastined to be together, it was fate. No matter what happens, the two of them will always love each other and belong together.
Spike--Passion and heat. This relationship seems to be full of heat, lots and lots of heat. Whether they're fighting or going at it, there's sparkage.
Riley--Boy meets girl. For the most part, this is boy notices girl, boy and girl date, they learn about each other, and feelings grow. Not really spectacular, but probably the most typical of real life.
Xander(not technically one of Buffy's boyfriend, but in the poll and why I decided to write this drivvel)--Friendship turns into love. Two people, who start out as friends and become really close, and find they care deeply for each other. They've been through a lot, and all that time as friends adds solidarity to the relationship.
So, I have always loved the idea of falling in love with my best friend, and actually got to do it in college. I haven't always liked the idea od Xander and Buffy, this is why I can get behind it now. Frankly, I think there's nothing more romantic then turning around and finding the one you can love is right there.
Does any of this make sense? Does anyone else see a relation between their ideal romance and which relationship of Buffy's they support?