It helps that mappers added a lot of functionality. IIRC Super Mario Bros. is the "best" you could do on base Famicom hardware. Later titles typically rely on mappers to allow for not only increased game size but potentially improved sound, and graphical effects like scrolling in multiple directions, saving, etc.
But yeah, gameplay wise this is pretty impressive. You can tell in a few spots it gets weird when there are a lot of sprites on the screen / moving.
Overall I think it's similar in quality to megaman3 etc. https://www.youtube.com/watch?v=dmuWCwTel-g
Yeah wow these games came a long way on that platform.