The Goliath when it comes to email of the two is most definitely Yahoo!, with Google's service playing the part of David. Or in other words, Yahoo! momentarily wipes the floor with Google, because it has been in the free email business ever since the beginning of the Internet as
we know it. Popularity is no a small thing to be having, so Yahoo is doing its best to keep its own intact and perhaps even raise it, little by little.
Indeed it does that, comScore.com's numbers on the matter indicate that the service provided by the Sunnyvale based company has risen by 3.12 percent the past year, but that is absolutely nothing compared to the figures that show in Google's part of the chart: a whooping rise of 53.60 percent. Of course, that doesn't mean very much when you're a service that has few users (not that it is Gmail's case per se, but its numbers are about twice or more lower than Yahoo!'s).
Taking into consideration a constant raise of at least the same number of users, Gmail will probably catch up with Yahoo by November 2010 and from there on end… it's not so clear of a future to be predicting. If Yahoo keeps rising and Google turns into the legitimate close runner up, I wonder where will the users be gathering and turn up from. It's either people will use both email providers, or one will lose in favor of the other and it's not a wild guess to find out who that will be.
If Google is able to pull this off, it will dominate the Internet in every possible way, sliding down the monopolistic path that so far hasn't proven to be the right one. Of course, if OpenSocial turns out to be a success, that is.