Unlike a disassembly of code that is written in a higher-level language like C, these old NES and Gameboy games were written in the assembly language you're seeing disassembled. Obviously there are no comments and labels, but the actual logic and the intent of the original developer is clearly communicated.

This allows for a really special type of awesome when you're working on fan translations and ROM hacks. You actually have the opportunity to analyze the work of the developers you idolized when you were younger, and celebrate a their clever hacks or curse them for their spaghetti code, 15 to 25 years later. Furthermore, you can contribute your own clever hacks to the code base.