It all depends on what you define as "best"
If you like drive-by installations and annoying alerts: Internet Explorer is best
If you like tabbed browsing and getting corrected as you type, thus proving yourself unable to write in English: Mozilla Firefox is best
If you like having compatibility with all lines of programming code, and want to tell everyone how much better your browser is like an annoying 12 year old rich girl: Opera is best
If you think that you might like getting slammed in the face by a browser that constantly pan-handles you to pay for extra services that you don't need, just so a billionaire can have more money: MSN is best
If you were aware when Netscape Navigator first came out and don't mind having a template that reminds you that you are outdated: Netscape Navigator is best
Personally, I like Mozilla Firefox because I am infallible and can't be corrected.