To tell you the truth I've always thought Tails was a girl myself. I had no idea it was the Americans that made him/her as a he for the show. That kind of sucks.
It would have been great had they made Tails a girl because he/she would be Sonic's partner/equal. And there wouldn't be any need for all these other silly girls like Amy or that fox looking chick. Whom are both inferior and weaker than sonic. And neither are helpful to him.
Though I have to admit that Tails being a boy is adorable and all. It just feels like him and Sonic are to much like Batman and Robin.
When they could have really made a difference in the female arena and gotten more girls interested in video games, had Tails been a girl. You have to admit the show would have been a lot more interesting that way too.
Though now everyone is used to Tails being a boy, changing the gender in a new series would probably annoy the old fan-base that have just gotten used to Tails being a boy. Oh well.