Anti-Trend said:
I'd bet ThePenguinCometh would probably suggest Slackware, which is also a good distro, albeit n00b-unfriendly.
Slackware is the King of distros, Slackware is God! All these other lesser distros are for kids and n00bs, Real Men use Slackware. Some distros are good for servers, some are good for the desktop, some are good for old hardware - Slackware does EVERYTHING. Are you a Slackware user or a mouse?
Seriously though, I don't actually know much about other distros as I used Slackware once and liked it so much that I didn't need to use any others. However don't fall into the (all too common) trap of getting a distro just because it has nice screenshots. Those screenshots are NOT of the distro, they're of the window manager - KDE, Gnome, Fluxbox or whatever. I don't know any reason why you couldn't take SuSE, Debian, Red Hat, Mandriva, Slackware, etc., etc., and have them all looking exactly the same as they all use the same window managers.
How the distros differ is primarily in their file structure, their preferred package manager and what packages they choose to install by default. Some may offers newer programs that offer cool features at the expense of stability and security while others prefer stability at the expense of the lack of features. Which is best for you really depends on what you need the computer for, how well you know Linux and how much time you are willing to spend configuring your system to your needs.
The real beauty of Linux is that you can easily pick and choose one without having to spend and money as distros that are only available for a price are in the minority. Also, if you understand the concept of partitions and multi-boot, you could run several distros on one machine while keeping your user files visible to all of them so there's no reason, unless you're not willing to invest the time needed, to not download several distros and try them all out and see which you like best.
As for which is the best distro? Simple!
Make your own!