Yea I've noticed the top 10 thing too. Nick stories have always been the most plentiful and I personally find him the easiest to write about. I stopped holding too much stock in the Top 10 anyway. It was fun at first, but now they don't really change much and in all honesty a few of those stories don't belong there.
But I've always written stories revolving around Nick and a girl. I don't think I could write as convinciengly about any of the other guys. I like to focus on relationships too. I have to have that female character in there too. I guess a lot of fics are pulling away from that now, but I'm very happy with the way I write.