Yahoo Mails is many times bigger than gmail in terms of users, and they also provide unlimited storage. So no, Gmail is far from being a leader
Yahoo rules in the matter e-mail. On gmail I receive ~25 spam per day (even i do not use that account very often and I NEVER registered anywhere using that account). In yahoo I get 2-3 spam messages per day and that is my main account (I use it everywhere).
you are right, actualy i have mail boxes in both of them i mean yahoo and gmail,but on gmail i registered not a long time ago,i have to say not bad servise, including more than 2000mb it makes gmail better i would say in google everything looks simpler.
Yahoo is the leader at the moment. Hotmail was leader earlier. Gmail will be the next leader in future.
The Gmail interface is easier to use and better on the eye than Yahoo. Also, I've received three messages of spam in my life with Gmail, but got about 20 a day with yahoo.
In search engine, I consider google is the leader but in email, I won't. Although gmail is also popular but it's not meant that they are the one leading on email services.