I agree that too many games just makes the system difficult to use, but on the other hand, there are many games that you might not even know about yet that you will really like.
I have a full set on my raspberry pi based system, but that uses 0.37b5, so there are only(!) Just over 2000 games.
If I didn't have a full set, I would never have discovered a few games which have become favorites.
I'm putting together a more conventional PC-based system, and it will be using a more up to date version of mame with a lot more roms.
I'm unsure how best to approach this, because I want the fullest selection possible, but at the same time I don't want to have 2000 versions of Mah Jong.
There are pieces of software that allow you to remove/hide certain types of game, so I'm going to look more into that.
My main concern is getting rid of the adult games because I don't want my five year old daughter discovering them by accident...
Maybe a similar tool could be used to get rid of other game types (like the aforementioned manifold iterations of Mah Jong)?