LogFAQs > #979243413

So the tricky thing about this question is that as far as the base hardware of the NES is concerned, Super Mario Bros. really is the peak accomplishment. Any game doing anything more advanced than that is using expansion chips included within the game cartridge itself to do things that the base console cannot do. You usually see these referenced when it comes to Japanese games having extra audio (like Castlevania 3, Gimmick, Lagrange Point, etc) but even something like Super Mario Bros. 2 or Contra is using one of these.