I went with Mastertronic for pioneering games that I could actually afford to buy on a regular basis. Which I did. I bought loads of them, including a few that remain personal favourites. Action Biker is usually one of the first games I play when I want to relive my C64 childhood.
That being said, I think there are better choices not on the list. Lucasfilm/Lucasarts, as mentioned by kynrek. They started out strongly with 3D fractal based aardvarks then later moved on to create the very best of graphic adventures. Infocom deserve a place as well for the very best text adventures, and Level 9 for squeezing nearly the same level of quality onto a loop of cassette tape.
My last mention, at least now before listening to the show, is Telecomsoft. Firebird/Rainbird/Silverbird. Again, I bought their games by the barrel-load. Elite, Cholo, Starglider 2, Thrust, Willow Pattern Adventure plus others. Fantastic.