Boxer lets you do the same for Dos games using DosBox. Wineskin lets you easily create Mac applications out of Windows games (and apps) using Wine. There are three absolute must have apps for the Mac when it comes to emulators, all free and OpenSource.
The Mac can’t be used for gaming? False! It has gotten a lot better in recent years and at any rate it just can’t be used for serious modern gaming, but if like me you’re a fan of old games anyway, a Mac offers you the most convenient and well designed emulation options out there.