OEM versions of games, supplied with 3D cards and the like, are usually the full version of the game, but without a box or a printed manual (it's usually on the CD). Sometimes the OEM version, is a "special" or cut-down version of the game (ie Half-Life ay One, or the version of Unreal that included the first 10 levels of the full game).
The Game Of The Year version, is usually the latest patched version of the game plus any extra's that the developer has released and, recently, any mods for the game that the developers like. There's usually nothing included that you can't download from somewhere if you have the "vanilla" version of the game.
The original is simply that, the first release of the game.
There was a man who claimed nothing is true, though he was later found to be lying.