Well, like everyone else said it depends on the girl. But generally older women like guys on cruiser-style, and younger girls like guys on sportbikes.
Me personally, I like to see a younger guy riding a cruiser. I ride a sportbike, and a lot of the guys are kinda cocky/annoying...as if twisting throttle is rocket science...lol (srry guys, no offense to anyone). I find that generally, guys who ride cruisers are way nicer and cooler, and laid back. And to see someone my own age ride a cruiser is very cool.
But that's just me..
~chai