Essentially what I'm doing is going through every game, one by one, curating a list of games that can be played in a competitive environment. So, I usually get together in a group of 4-8 friends at the weekend, and just hit random, and compete in whatever game comes up. As long as it has a competitive mode of some kind (easy enough with fighting games, sports games, racing etc) or a single player high-score or time trial mode. We'll usually get through 15-30 games a night, and build a leader board as we go (4 points for 1st place, 3 for 2nd etc). Yes, we're nerds, but we started this as a way to get together more after covid lockdowns ended and it's been great fun.
I originally started doing it by downloading the complete sets for each system, but that was taking forever, because we'd end up skipping load of RPGs, or strategy games etc. So now I'm going through each game, and marking whether it fits into our 'RetroMania' collection or not. If I could filter the games database (website) by games that I haven't yet added to a collection, it would make it easier for me to see which games I haven't yet 'processed'.
I realise this is all very niche and unlikely to be useful for anyone else, just thought it was worth asking!