I personally think it affects how attracted we are to a guy. I am obsessed with the smell of Axe and Old Spice xD I love other stuff yes, but damn when I smell that stuff I just wanna rip your clothes off and do very naughty things to you.
Horrible example, but example non the less: One of my best friends is a guy, and I personally would never date him (various reasons don't wanna go into). However after already knowing him a year, he once came out of the shower right before we hung out and he smelled like Axe and oh my damn, I wanted to just smell him all day and kiss him or something. Then I remembered who it was and knew I couldn't.
I totally love cologne smell... I fall for cologne smell more often than I should! About two years ago I was deeply attracted to some guy that used le male by jean paul gaultier even now when I smell that cologne it make me remember that guy... Other one that make me fall on my knees is fierce by abercrombie!
A guy who smells good is a turn on... MAJOR turn on. But that doesn't mean I'd actually fall for him because of how he smells. It would just form some of the initial attraction. It can't substitute actually spending the time to get to know him.
I personally do like it when a guy smells good, but do you mean a natural smell or cologne? Because I LOVE it when a guy uses cologne, that instantly makes me attracted to them, even before I see them, lol. Hope this Helps! =D