In fact, another one of Carmack's contributions to PC gaming was porting Super Mario 3 to the PC and demoing it to Nintendo as a proof of concept for smooth pixel sized scrolling, which was something that PCs were very poor at. His approach was to basically do a graphical diff frame by frame and only render the parts of the screen that changed, whereas all the other home computers I mentioned and even gaming consoles like the NES and Sega Master System had dedicated hardware for scrolling sprites.
Nintendo did not go forward with Carmack's proposal, wanting to keep their games exclusive to their own platform, but Carmack and id Software did manage to use that technology to develop Commander Keen. Prior to Commander Keen there were maybe 3-4 PC games that had any kind of pixel scrolling whatsoever and it was fairly limited.