i guess its different with every guy but I personally see it as something special. as in id rather be in a fully committed relationship to the girl before going through with it because id rather make the first time experience great and memorable for her. generally though, girls who are virgins are a lot more emotional over it there first time so id like to have her trust and make sure she is comfertable. in essense I think it makes you feel good to know that she chose you to be the one to take it from her and share it together.
on the other hand some guys like it as an ego boost to be able to know they was the first to take their virginity but don't always value it as much. some guys would rather just have straight sex with an experienced girl though because they would want to have a good time without all the extra emotions that would be involved from a girl that gives her virginity to you. the way I see it is, experience can always be gained and nothing would compare to sharing the first time together. :)
It's not so much the "taking" of the virginity that guys are attracted to. It's the fact that they know that they are the first. Which is like, "I'm the first guy to climb to the top of this mountain." or "I'm the first guy to be "allowed" to do something that no other guy has been "allowed" to do.
For most guys it's not some evil obsession. It's not like they wear, "I'll take your viginity" tee shirts or something. It's just something that a guy will never forget. He was the first to have a girl in her life. He also knows, he won't be the last.