TL;DR: Some way to differentiate canonical franchise entries from noncanonical ones would be awesome.

First off, I love that IGDB accepts and maintains data about ROM hacks, fan games, and other "unofficial" titles. It really helps the platform's position and usability as a database for all games of all kinds.

That being said, when looking through the search results for a franchise like Pokemon, there are an incredible number of these unofficial games mixed into the results, many of which are built off of the existing, official games. There's nothing (as far as I can tell, anyway) in the metadata outside of the game's free text description that separates something like Pokemon Blaze Black (a ROM hack) from Pokemon Black or Pokemon Black 2 (both official games).

I think it would be great to have a tag of some kind that denotes the work as unofficial or fanmade. I see that ROM hacks are commonly listed as "mods" of their base game, but this doesn't encapsulate games made in tools like RPG Maker or Unity or games made using their own custom engines. I would also argue that ROM hacks and mods as they're known in the PC gaming scene are two different concepts, but that's a subject for a longer debate.