The Mac OS
Apple operating systems were always intended to be simpler than the competition -- MS-DOS, Windows or Linux -- and that approach is readily apparent, whether it's Mac OS System 7 or Mac OSX, software largely derived from Jobs' work at NeXT. Windows fans sometimes criticize it for lacking customization options, but that's really the point. By making it as simple and easy-to-use as possible, the Mac OS maintains a strong reputation for accessibility and stability, something that couldn't always be said of Windows through the years.
