Comments in games varied a lot. The coin-op folks did pretty well, and most of the systems code for the computers was well commented.
Lots of game cartridges had very few comments. While this was in an era where comments would slow down your turnaround time, I think much of it was the fast development pace and the fact that once a game had shipped, it was done. It was in ROM, real mask ROMs that were not patchable, and no one would ever be going back to that code again.
I did kind of follow through and made "sort of a game" for it: https://github.com/mrspeaker/plops Though it lacks polish, it does have a theme tune!