>>3
Sane defaults hits the spot. Add easy installation, beeing debian based, a good community, beeing available in several desktop flavors and a stable release cycle.

• Debian-based: Well, it uses apt, and apt is simply wonderful. Having a huge, easily searchable software repository that allows you to find software you need and to download and install it with only 4 or so mouse clicks (Or two shell command, if you prefer that) is awesome.
• Easy installation / sane defaults: Put CD in. Boot. Press install. 30 minutes later, everything works. It even managed to detect the wireless usb stick on my PC and the wireless card in my Laptop. And after booting up, you don't have to spend an hour or so to make the system work properly. You can just get to work. And if some stuff does not work (MP3's for example) theres a nice script (automatix) that installs all that stuff for you.
• Release cycle: New version every 6 months. It's just a nice thing to know.
• Good community: Gentoo has an awesome community. Ubuntu has, too, probably not as awesome as gentoo's but still awesome. New users are normally well recieved, the forums are full of helpful posts.
• Several desktop flavors: If you like gnome, use Ubuntu. Like KDE? Use Kubuntu (I do that). XFCE? Xubuntu.