k... gotta pitch in some...
1. MacOS X
2. NeXTStep/OpenStep/Rhapsody
3. BeOS
4. FreeBSD
5. Mac OS 9
6. Linux and friends
7. Microsoft Windows 2000/XP/Server 2K3 (NT 5.x)
8. Darwin (since it is distributed freely separate of OS X)
9. DOS w/ Windows 3.1
Yeah, I know NeXTStep/OpenStep became Rhapsody which became OS X, but there's important differences that make it "all new".
Linux is a perfect server OS. It *isn't* ready for desktop. UI and graphics framework are only two problems. Also, software installation, hardware support (that is, more companies need to support it openly), and general usability need to improve.
X11 is allright for server use, where network transparancy and other factors win out over graphic abilities. A server doesn't need eyecandy. X11, however is hopelessly outclassed by other desktop OS display layers.
Give it some time, guys... and... also, give a little. Support projects that push Linux distros past their UNIXy heritage. Stryker's CalyptOS, and mine and Jeffberg's CthulOS/Next Generation Desktop are prime examples. Use the Linux kernel to make a nice, user-friendly desktop OS... perfect. Linus made a good, solid, and quick kernel. Give it an OS that's worthy of what it can do instead of dragging it down with the outdated UNIXness.