On the flip side, guys can't shouldn't try to sing like girls.
As I said before, I appreciate growling, but at the same time I like something different. Hearing a pure operatic voice where you usually hear growling is interesting to me. Its the dichotomy that I like. Many of the bands that use female vocalists also have male vocalists that do growling (again, listen to Epica's Cry for the Moon). I've heard this style described as Beauty and the Beast, and I can't argue with that.
Some bands use male vocalists whose voices are a bit cleaner, but still more in line with what you expect from rock/metal. Listen to Nightwish's cover of Phantom of the Opera. Or a band called Delain, but I can't think of, offhand, a particular song.
Generally speaking though, I like bands that can mix it up. Like 5FDP has clean vocals as well. Or a band that I heard when they opened for Epica, and I've since become a fan of...Scar Symmetry.
The Agonist, featuring a female growler, also opened for Epica. Though I listened to them a bit on youtube, I didn't like it much. However, I was much more impressed with them live.