So I've started playing the vertical games which MAME 0.37b5 supports and I've learned a few things.

First, while the Raspberry Pi Zero is incredibly powerful compared to the CPU of the arcade games, it is also having to emulate the graphics and audio processors as well.  So while the majority of the games are playable, the game isn't displaying all of the frames and the sound is choppy or worse.  The lower fps actually turns out to not be a big deal, but it's difficult to listen to the sound (at least through headphones).

Given the huge number of games I can afford to be ruthless pruning down the list.  So anything which isn't running at full speed (or has other issues) won't make the first cut.  And even if the game does play perfectly it also must be fun to play.  There's no point in including games which I won't want to play again.

I have flagged the games the "best of" lists on arcade-museum.com (aka KLOV) and the games included on a 60-in-1 vertical multicade.  These might be exceptions to the full speed rule.

It's also amazing to go through these games and re-discover some while playing others for the first time.