Given the option, I always play both, but I usually start with my own gender.

I almost always play females as I am in real life. However, sometimes I like to look at a big strong handsome guy who hacks and slashes a bloody path through an MMO. I nearly always make -one- for when I get tired of looking at useless bikini armor. :P

I always choose my own gender when playing a game. My entire family enjoys playing games so we usually have plenty of both genders (depending on the game - no my kids don't play DDO). I just don't feel the need to see it from the other side. LOL. Now my husband on the other hand, for SOME reason he likes to create girl characters...he says so that *I* can play that character too...likely story. =)

I'm a guy. I play female toons. Why?
Well, the picture on the screen is Not me - it is a toon in the game. When you're playing the game the normal view is from behind your toon, which means you spend hours looking at your toon's butt. And if I'm going to spend hours looking at a butt - it's going to be a Female butt Thank You Very Much!
BTW, I'm married and have been 32 years.

Bit of both, really. My main/first char on WoW was male, but now I prefer to play female characters. They tend to look much cooler when clad in their hard-earned armour than male ones do. Also, if I'm going to be running around for hours, it doesn't hurt to have something to look at.

What!? I can sense you judging me...

I'll usually play as a male(like myself) but if I'm given the option I'll sometimes pick a female to mix it up a bit.

My main in WoW is male (like myself), but my twink is female.