Most people seem to think Google/Gmail is by far the best. I think other feedback will confirm this.
I don't like it at all, I find the interface clumsy, and as an IMAP type email, it doesn't interface well with some email clients.
It's spam filtering is excellent, and it has massive, or unlimited, storage.
There are other free emails such as Hotmail, Yahoo, and many others, unfortunately they tend to lack credibility if you use them for business purposes specially if combined with a silly name (I got an employment application from a lady who called herself prettytitty@a yahoo domain, it doesn't conjure up a good image), and a lot of emails divert emails from those domains into spam.