I think linux is a great OS, and some of the packages is really easy to install. I use
SUSE 10, but I know other people would tell you to stay away from it. It's the same about ubuntu. Linux is great for reasonable things, but when it comes to the best games, you have to work to find out how you should get it work.
You can find a linux distro for most computers.
I won't tell the computer requirements since I first don't know them, and second I can't find them. The only thing I know is that graphical suse linux 10 requires or recommend 128MB ram(half if you don't want graphical interface)
It's many distros because linux is opensource and too many people improves it to only use one distro. Also someone needs to don't choose what you want, and it's impossible with so many developers to have one default configuration.