Yahoo, Hotmail, and Gmail are the top 3 most used. I use Gmail, and it's never given me any problems. Yahoo, I had an account and it was kinda complicated and often I had problems. Hotmail, I also tried, that was same deal, a lot of problems. I've had Gmail for about 4 years now, and love it. I Highly reccomend Gmail.
I would say that right now you are best off with Outlook.com. This is Microsoft's take on email. It is an offshoot of hotmail.com and is absolutely superb. In the past Outlook was the cream of the crop only used by people paying for their address/domain name. Now Microsoft has made it free, and it is extremely efficient. The viewing window is well laid out, you can send huge attachments, offers about 7GB of online storage. If you haven't seen the you're getting Scroogled ad, you should look it up. Don't use Gmail, use common sense and get yourself an Outlook Account.