Everyone I know has a hotmail account. It's everyone's throwaway-give-to-spammers account. Those same people have all slowly migrated to using their Gmail address for their most important emails. So if you look only at number of users, Gmail might be behind. But if you were to know the number of active users, I would guess Gmail is way ahead.
Heh, I think it has something to do with where you are. I don't know a single person with a hotmail account, know 2 with a yahoo account, and everyone else has a gmail account. (So, what? 100+:2:0?)