You could use Bootcamp to install Ubuntu. The Unity DE behaves a lot like OS X, just more organized, customizable, skinnable, and easier to use. Also, see virtual desktops.
The Linux port of SRB2 works there, as well as many games and software that are never ported over to Mac. I would say I see far more software on either Windows or Linux than Mac by a long shot, and that's one of the reasons I don't ever want a Mac PC. (Besides how messy OS X looks as a desktop and probably is under the hood too, but that's an entirely subjective matter.) It's also slowly becoming more and more locked down as Apple slowly rewrites all the open-source licensed portions of the OS; do not want.