I said that the majority of my characters are the same sex as me. But there's a reason for this, and it isn't any aversion to cross-gender roleplaying. It's because:
(1) In most of the settings which have inspired D&D worlds (all the historical ones, and most of the fantasy ones), exploring subterranean vaults, slaying dragons, doing battle with evil, etc., are traditionally roles for a certain gender. Specifically, the male. Absent specific DM instructions to the contrary I expect something similar in the campaign world. That doesn't mean there shouldn't be the occasional Jeanne d'Arc. But Jeanne d'Arc would not have acquired her particular mystique if she didn't pursue a calling that was unusual for women. In order to preserve this flavour aspect, such characters shouldn't be a dime a dozen.
I therefore think it appropriate the the majority of PCs be male, unless the DM has specifically decided to toy with gender relations and roles in the campaign world and do a setting in which women are as likely as men to become adventurers.
I do sometimes (maybe 1 out of every 3-4 characters) create a female character, for variety's sake, but I don't want to make them too common.
(2) I also have a particular sex, namely male.
Since (1) and (2) happen to coincide, it follows that about 70% of my characters are male.
I'd be interested to see the results of this poll broken down by respondent's sex. I wonder, are male players more likely to create female characters than vice versa? Are the people who more often than not play cross-gender mostly women and girls applying reasoning similar to me?