Perhaps most notably, the lack of support for the PC-8801 outside Japan means that we missed the sequel to Super Mario Bros. No, not The Lost Levels. Even lost-er.
Hudson Soft made an agreement with Nintendo to port their arcade/Famicom hits to the PC-8801 system. It was in this way that fairly ugly, slow versions of Mario Bros., Ice Climber, and Excitebike appeared on the computer system with Hudson's name on the title screens. For the most part, they kept the games as accurate as they could. But for Super Mario Bros., for some reason, Hudson decided to create a new game. They retitled it Super Mario Bros. Special and went about designing new levels and inserting enemies from other games. The hammer weapon, barrels, and fireball enemies from Donkey Kong appear in this game, as do elements of Mario Bros. ... which actually leads us to wonder why that stuff didn't appear more in the Nintendo-developed Super Mario Bros. series.
The PC-8801 was clearly not designed to run Super Mario Bros. Hudson's Special is slow, choppy, flickery, and has a severely reduced color palette. Most importantly to gameplay, it no longer scrolls smoothly, instead moving one screen at a time like The Legend of Zelda.
There shouldn't be any need to explain the appeal of a largely undiscovered Mario game in general, but there's a certain compelling quality about one that's not quite right. It's the same feeling that we get from seeing things like the Kaizo Mario remixes or Nintendo's own Super Mario Bros. 2 (the Japanese version). The basic nature and rules of the game -- stuff we take for granted -- is all messed up in games like these. We can't trust the innate sense we develop for understanding Mario's world. Also the Hudson bee's in there, and that's pretty weird.