I have at least two dozen emulators on my MAME pc and don't use most of them.
I was in the mindset of having it play
absolutely everything possible 
There is some novelty to playing a gameboy game on a 32" screen, but it wears off after about 2 minutes.
I'd recommend: Nebula's Sega Model 2 Emulator - plays 3D games not playable in MAME
Makaron - plays Naomi games that won't be playable in MAME for many years to come
Future Pinball - Much easier to install and better looking than Visual Pinball, but not nearly as many re-created tables.
Vivanonno - Plays the Ridge Racer series. Probably not a fit for your cab, but I play it more than anything else on my driving cab.
Demul - plays Naomi, Atomiswave & Naomi 2. Just started messing around with this one. For fighting games, I've had better results
with Makaron so far, but Makaron doesn't emulate the Atomiswave hardware or support light guns.
Occasionally, I'll load a Sega Genesis (Kega Fusion) or Atari 2600 game for the sake of nostalgia, but I rarely play it for more than 5 minutes.
In the Mala forum, in one of the stickies, is a writeup by UncleT about installing a bunch of emulators to work with Mala.
It includes a big list of emulators and tells you everything you need to know to get them up and running.
Lot's of good info there, even though you aren't planning to use Mala.