I went with Super Mario world because if you asked me in 1990 that would of been my vote. That being said the most important game for future of PC gaming that was released in 1990 was Commander Keen in Invasion of the Vorticons as it was a side project of John Carmack and it success led John Carmack and others to quit working for Softdisk and create ID software which went on to basically create the FPS genre with Wolfenstein 3d and made it mainstream with Doom. Commander Keen also a fun game on it own and another example of John Carmack genius because smooth side scrolling games really only existed on consoles and not PC before he created a way to do it on PC. He actually originally created the code to try to sell Nintendo on porting Mario to PC but Nintendo was not interested so he made Commander keen instead.