Besides ports of their arcade games to Atari systems, Nintendo kept most of their games on their own systems. However before the late 90's, they weren't afraid to release some things on PCs. Super Mario Bros. Special was created by Hudson for some Japanese only computers.
This is the game on the X-1 computer. Very similar to the original NES game, but the colors are a bit different like yellow becoming very dominant for some reason. .
And Fire Mario looks just like Luigi as well...
While looking very much like the original game, the levels were quite different. The screen would also move in turns instead of it following smoothly, though you could not run behind the screen in the NES game.
This is the version ported to the NEC PC-88. While essentially the same game as the X1, it featured much different color tones, graphics would flicker often, and didn't run nearly as smooth as the X1 or the NES.