MPlayer plays a huge number video formats, many using OpenSource CoDecs included with MPlayer (such as FFmpeg's libavcodec for MPEG 1, 2 and 4). Proprietary CoDecs such as RealPlayer RealMovie can be played by using their MicrosoftWindows DLLs and the avifile library (obviously this is less than optimal so use MPEG 4 or H.263 for all your DVD rips ;-)). MPlayer can play MP3 and OggVorbis, so you can also play video with sound encoded with those CoDecs. It's suboptimal for DVDs as it does not support DVD menus.
MPlayer has normal GUI, but can also be fully controlled from a remote control, keyboard, joystick or line-based protocol. Joystick might seem a bit useless, but you could use a wireless gamepad or a PlayStation2 console remote.