Below are a few charts indicating market share between Google, Yahoo and Microsoft from Hitwise.
Earlier this year, Techcrunch did their own comparison and Gmail ended up coming out on top in their testing/research as well:
“Overall we prefer Gmail over all other webmail applications because performance (speed) is consistently fast, and emails can be tagged making search much more effective. They also offer more storage and other features, and it’s free. However, Yahoo and Live Hotmail offer more mainstream Outlook-like user interfaces (although Live Hotmail does not allow you to access other email accounts from their application), whereas Gmail takes some time to get used to. If you are looking for speed and tagging is important, Gmail is for you. If you are looking for the closest thing to Outlook online, go with Yahoo Mail. “
Google Up 43% in 2008!
July 2009 – (Source TechCrunch)
Gmail is now the third largest Web mail service in the U.S. In July, Gmail nudged past AOL Email with 37 million unique visitors compared to 36.4 million for AOL, according to comScore estimates. That puts Gmail within sight of the No. 2 player, Windows Live Hotmail, which has 47 million unique visitors. Yahoo Mail still at top with 106 million monthly unique visitors.