In my opinion, the best email service is Gmail, because of the following reasons.
a) Because it organizes mail with labels, not folders, one email can have several labels instead of having it stuck in one folder.
b) It's search is extremely powerful, and it never fails to find an email. This is very useful if you get many emails per day.
c) You can customize your mail with themes easily to give your email a different look and feel. You can even have it give a random theme every day so you won't ever get bored.
d) Filters can get your email out of the way and into where you really need. This can be useful if you want to separate your personal email from your business email. You can do this by setting up a filter with simple instructions.
e) If you use Google services, you're in luck because Gmail integrates with Google Calender, Docs, and more. All you gotta do is go to Gmail labs.
I believe that Yahoo! Mail gives unlimited storage for users, so if you looking for storage, go to Yahoo! good luck in your quest!