Hah, that’s sloppy on my part. I pick Streets of Rage by random and quickly looked up some examples, and having the compilation undercut what I was trying to say. Of course the compilation would not be part of the release group.
Generally, I’ve been trying to fill out “Work” entries with game’s soundtracks. So hierarchy would be
Work series (game series) => Work (game) => Work (song)
So any recordings of any game soundtrack release are based on the individual works. “Recordings” become a weird concept when, essentially, encountering music in a game is a new performance every time.
What I’m thinking then is that, Work series of video game series and Release group series of video game series might exist together. In this scenario, the Work series exists over the Release group series, so the Release group series would use the “subseries of” connection to the Work series.
Grouping game soundtracks together in a release group despite different releases over time… like the Streets of Rage example I made pretty badly… makes sense then.