It's still quite impressive to fit such a lengthy and fun game into 508KB without any procedural generation, just tight assembly and clever use of bitmaps. This is programming art.
This is largely a lost art because of several bad paradigms that have become very popular in recent years, making software exponentially worse in the process. In the old days, it was common and NES games were even smaller than SNES games because the graphics were much less complex. I believe Super Mario Bros 3, which many people still insist was better than Super Mario World, actually fit into 32KB.
