I remember running Half Life 2 on some card way below the recommended spec. There was some commandline switch to run the game in DX7 or DX8 mode, turned everything to lowest and resolution like 640x480. Looked worse than Half Life 1, but at least was somewhat playable.
Some people managed to run Doom 3 on Voodoo 2/3 cards, applying some patches and resizing the game textures, etc...
I managed to run Doom 3 on a Creative GeForce 2 MX DDR using the patches for Voodoo 2 and doing the same trick of resizing textures. The game was playable, except for the boss guarding the soul cube.
I was one of the poor bastards playing Half-Life 2 on a Voodoo 3 around that time... stuttered like crazy, required setting everything as low as possible and then some with console commands... ran at an admirable ~20fps, but I was used to worse on my n64, so I just sucked it up lol.
