i’ve done some excel experiments – here’s a list of the games that ARE in FBAnext but are NOT in mame2003 (parent roms ONLY):

1945k III
4 player input test [Demo, 4 player input test cartridge]
7 Ordi (Korea)
A.B. Cop (World, FD1094 317-0169b)
A.D. 2083 [Incomplete Sound]
Agress
Air Assault (World)
Air Attack (set 1)
Alien Challenge (World) [Imperfect sound]
Alien Invaders [preliminary sound]
Alien Sector
Arcadia (NMK)
Asura Buster - Eternal Warriors (Japan) [Imperfect SND, freezes on first boss]
Back Fire (Tecmo, bootleg)
Backfire! (set 1)
Bang Bang Busters (2010 NCI release) [Prototype]
Battle Garegga (Europe / USA / Japan / Asia) (Sat Feb 3 1996)
Bee Storm - DoDonPachi II (V102, World)
Best Of Best
Bestri (Korea)
Bikkuri Card (Japan)
Birdiy
Bomb Kick (set 1)
Bongo
Boogie Wings (Euro v1.5, 92.12.07)
Buccaneers (set 1)
Bullet (FD1094 317-0041)
Bygone [Imperfect sound]
Cannon Ball (Pacman Hardware) [wrong colors]
Catacomb [Bad Colours]
Chain Reaction (World, Version 2.2, 1995.09.25)
Chance Kun (Japan)
Chaos (PGM Demo) [Demo, Demo Game]
Chaos Demo (CPS-1) [Demo]
Chaos Demo (Neo Geo) [Demo]
Charlie Ninja
Chip n Dale (Intro demo) [Demo, You must use the Universe BIOS and set region to Japan AES]
Choko (010820 Japan)
Choky! Choky!
Choplifter (8751 315-5151)
Choutetsu Brikin'ger - Iron clad (Prototype) [Prototype]
Codename - Blut Engel (2006-01-19) [Homebrew]
Columns (Neo Geo) [Homebrew]
Combat Hawk
Come Back Toto
Cookie & Bibi (set 1)
Cookie & Bibi 3
Crazy Fight
Crouching Poney Hidden Dragon (DEMO) [Homebrew]
Crusher Makochan (Japan)
Cyber Tank (v1.4)
Dambusters (US, set 1)
DarkWing Duck (Intro demo) [Demo, You must use the Universe BIOS and set region to Japan AES]
Date Quiz Go Go (Korea)
Deer Hunting USA V4.3
Demon Front (V105)
Desert Breaker (World, FD1094 317-0196)
Diet Go Go (Euro v1.1 1992.09.26)
Digger Man [Homebrew]
DoDonPachi Dai-Ou-Jou (V101, Japan)
Dolmen
Double Point
Dr. Tomy
Dragon Bowl
Dragon World 2001 (V100, Japan) [Bad sound?]
Dragon World II (V110X, World)
Dragon World Pretty Chance (V101, Japan) [Bad sound?]
Duck Tales (Intro demo) [Demo, You must use the Universe BIOS and set region to Japan AES]
Dynamite Dux (set 2, FD1094 317-0096)
Dynasty Wars (US set 1)
Egg Hunt
Espgaluda (V100, Japan)
Excelsior (set 1)
Explosive Breaker
Fantastic (Galaga conversion on Galaxian hardware)
Fantasy Zone II - The Tears of Opa-Opa (System 16C)
Fever SOS (International, ver. 98/09/25)
Fighting Basketball
Final Tetris
Flying Tiger (set 1)
Frog Feast (CPS-1) [Homebrew]
Frog Feast (Neo Geo) [Homebrew]
Frog Feast (PGM) [Homebrew]
G-LOC Air Battle (US)
Galaga Demo (set 1) [Homebrew]
Galaxy Force 2
Gals Panic S3 (Japan)
Ganbare! Marine Kun (Marine 2K0411 JPN)
Garogun Seroyang (Korea)
Ghost Busters (Intro demo) [Demo, You must use the Universe BIOS and set region to Japan AES]
Ghostlop (prototype) [Prototype]
Gouketsuji Gaiden Legends (USA, ver. 95/06/20)
GP Rider (World, FD1094 317-0163)
Grasspin
Guardian
Gunbarich
Hammer Away (prototype) [Prototype]
Happy 6-in-1 (V102 - V101MK, China)
Heuk Sun Baek Sa (Korea)
Honey Dolls
Hot Mind (Hard Times hardware)
Hyper Crash (version D)
Hyper Street Fighter II: The Anniversary Edition (040202 USA)
Idol Mahjong - final romance 2 (Neo CD Conversion) [Hack]
Jackie Chan in Fists of Fire
Jockey Grand Prix (set 1)
Joe & Mac Returns (World, Version 1.1, 1994.05.27)
Joinem
JoJo's Bizarre Adventure: Heritage for the Future / JoJo no Kimyou na Bouken: Mirai e no Isan (Japan 990927)
JoJo's Venture / JoJo no Kimyou na Bouken (USA 990128)
Jonas Indiana and the Lost Temple of RA (20050717) [Homebrew]
Jumping Pop (Nics, Korean bootleg of Plump Pop) [Imperfect graphics]
Jumping Pop (set 1)
Jyangokushi -Haoh no Saihai- (990527 Japan)
Kero Kero Keroppi's Let's Play Together (USA, Version 2.0)
Ketsui Kizuna Jigoku Tachi (Revision 2?, Japan)
Knights of Valour 2 (V107, 102, 100, Hong Kong)
Knights of Valour 2 Plus - Nine Dragons (VM205XX, China)
Knights of Valour Super Heroes Plus / Sangoku Senki Super Heroes Plus (ver. 101) [Imperfect Protection Emulation]
Knights of Valour: Yi Tong Zhong Yuan / Sangoku Senki: Yi Tong Zhong Yuan (ver. 201, China) [Imperfect Protection Emulation]
Knuckle Bash 2 (bootleg)
Konami Test Board (GX800, Japan)
Kong (Donkey Kong conversion on Galaxian hardware) [Bad Colours]
Koro Koro Quest (Japan)
Kozure Ookami (Japan) [Imperfect Graphics]
Lady Master of Kung Fu
Last Hope CD Beta (Neo CD conversion) [Hack, Imperfect graphics]
Last Survivor (FD1094 317-0083)
Lethal Enforcers (ver UAE, 11/19/92 15:04)
Live Quiz Show
Lord of Gun (USA) [Imperfect graphics and sound]
Lover Boy
Lucky Today [Bad colours]
Mahjong G-Taste
Mahjong Hot Gimmick Integral (Japan)
Mang-Chi
Martial Masters (V104, 102, 102, USA)
Match It II
Matrimelee / Shin Gouketsuji Ichizoku Toukon (NGM-2660) (NGH-2660)
Mega Blast (World)
Meijinsen
Metal Saver
Metal Slug 4 (NGM-2630)
Metal Slug 5 (JAMMA PCB)
Metal Slug 5 (NGM-2680)
Michael Jackson's Moonwalker (set 3, World, FD1094/8751 317-0159)
Mighty Warriors
Mighty! Pang (001010 Euro)
Miss Bingo
Miss Puzzle
Monster Maulers (ver EAA)
Monsters World (bootleg of Super Pang)
More More
MTV Rock-N-Roll Trivia (Part 2)
MuHanSeungBu (SemiCom Baseball) (Korea)
Multi 5 / New Multi Game 5 (set 1)
Multi Champ Deluxe (ver. 0106, 06/01/2000)
Nandemo Seal Iinkai
Neo 2500 Demo [Demo]
Neo CastleVania Demo [Homebrew]
Neo Geo CDZ system [System - media selected seperately]
Neo No Panepon (beta) [Homebrew]
Neo Pong (ver 1.1) [Homebrew]
Neo System Check (ver 1.0b) [Demo]
Neo Thunder [Homebrew, sebastianmihai.com]
NeoGeo 2-Player Tetris [Homebrew]
NeoGeo 3D! Demo [Homebrew]
NGEM2K (beta 2006-01-18) [Homebrew]
NGF Transparency Demo [Homebrew, redarmor.net]
Ninja Kazan (World)
Noboranka (Japan)
Orbs (10/7/94 prototype?)
Oriental Legend Special Plus / Xi You Shi E Zhuan Super Plus (ver. 205) [Incomplete Dump]
Oriental Legend Super (V101, Korea) [Imperfect Protection Emulation]
Osman (World)
P-GeMeni (060123) [Homebrew]
Pairs Love
Pang Pang
Paparazzi
Party Time: Gonta the Diver II / Ganbare! Gonta!! 2 (World Release)
Planet Probe (prototype?)
Pochi and Nyaa
Pocket Gal Deluxe (Euro v3.00)
Pocket Gals V.I.P (set 1)
Poker Night [Homebrew]
Pop Bingo
Pop's Pop's
Power Drift (World, Rev A)
Primo Demo [Homebrew]
Progear (010117 USA)
Puzz Loop 2 (010302 Euro)
Puzzle Break
Puzzle Club (Yun Sung, set 1)
Puzzle Star (V100MG) [Incomplete dump]
Puzzli 2 (V100) [Incomplete dump]
PuzzLove
Quiz Olympic
Quiz Tonosama no Yabou 2 Zenkoku-ban (tonosama 2 950123 Japan)
Racing Beat (World)
Racing Hero (FD1094 317-0144)
Rack + Roll
Rage of the Dragons (NGM-264?)
Raiden DX (UK) [Coin inputs require holding down]
Rail Chase (World)
Rainbow Islands (new version)
Red Earth / War-Zard (Euro 961121)
Riot
Robocop (Intro demo) [Demo, You must use the Universe BIOS and set region to Japan AES]
Rock Duck (prototype?) [incorrect colors]
Rock'n 3 (Japan)
Rock'n 4 (Japan, prototype)
Rock'n Tread 2 (Japan)
S.V.G. - Spectral vs Generation (V200, China)
Samurai Shodown V / Samurai Spirits Zero (NGM-2700)
Samurai Shodown V Special / Samurai Spirits Zero Special (NGM-2720)
Saturn
Schmeiser Robo (Japan)
Scooter Shooter
Scorpion (set 1) [Incomplete Sound]
SD Fighters (Korea)
Search Eye (English / Korean / Japanese / Italian)
Search Eye Plus V2.0
Sengoku 3 / Sengoku Densho 2001
Shadow of the Beast (Neo Geo demo) [Demo]
Shinobi / FZ-2006 (Korean System 16 bootleg) (ISG Selection Master Type 2006)
Silver Millennium
Snapper (Korea)
SNK vs. Capcom - SVC Chaos (JAMMA PCB, set 1)
SNK vs. Capcom - SVC Chaos (NGM-2690)(NGH-2690)
Snow Brothers 3 - Magical Adventure [Bootleg]
Soldam
Sonic Boom (FD1094 317-0053)
Space Bomber (ver. B)
Space Raider
Spectrum 2000 (vertical)
Spiderman (Intro demo) [Demo, You must use the Universe BIOS and set region to Japan AES]
Squash (Ver. 1.0)
Street Fighter (US set 1)
Street Fighter II' - Hyper Fighting (street fighter 2' T 921209 ETC)
Street Fighter III 2nd Impact: Giant Attack (USA 970930)
Street Fighter III 3rd Strike: Fight for the Future (Euro 990608)
Street Fighter III: New Generation (Euro 970204)
Street Fighter Zero (CPS Changer, 951020 Japan)
Street Fighter Zero 2 Alpha (960826 Asia)
Strike Fighter (World)
Success Joe (World) [Incomplete sound]
Sukeban Jansi Ryuko (set 2, System 16B, FD1089B 317-5021)
SunA Quiz 6000 Academy (940620-6)
Super Bishi Bashi Championship (ver JAA, 2 Players) [Imperfect gfx (bad priorities)]
Super Model
Super Monaco GP (World, Rev B, FD1094 317-0126a)
Super Trio
Super Triv [No sound]
Surprise Attack (World ver. K)
SWAT Police
Taisen Hot Gimmick 4 Ever (Japan)
Tang Tang (ver. 0526, 26/05/2000)
Teenage Mutant Ninja Turtles (Intro demo) [Demo, You must use the Universe BIOS and set region to Japan AES]
Tenchi wo Kurau II - Sekiheki no Tatakai (CPS Changer, 921031 Japan)
Tetris (D.R. Korea) [Wrong colors]
Tetris / Bloxeed (Korean System 16 bootleg) (ISG Selection Master Type 2006)
Tetris the Absolute The Grand Master 2
The Gladiator - Road Of The Sword / Shen Jian (V101) [Incomplete Dump]
The Killing Blade (V109, China)
The Killing Blade Plus (V300)
The King of Fighters 2001 (NGM-262?)
The King of Fighters 2002 (NGM-2650)(NGH-2650)
The King of Fighters 2003 (Japan, JAMMA PCB)
The King of Fighters 2003 (NGM-2710)
The Lost Castle In Darkmist
Thunder Heroes
Thunder Hoop (Ver. 1)
Time Fighter (Time Pilot conversion on Galaxian hardware) [Bad Colours]
Time Scanner (set 2, System 16B)
Time's Up Demo [Homebrew]
Toppy & Rappy
Treasure of the Carribean [Prototype]
Triple Draw Poker [Bootleg]
Trophy Hunting - Bear & Moose V1.0
Turkey Hunting USA V1.0
Twin Action
Twin Adventure (World)
Twin Falcons
Twinkle
Uncle Poo
unknown Pac-Man gambling game
V-Liner (set 1)
Varia Metal [Imperfect graphics]
Wally wo Sagase! (rev B, Japan, FD1094 317-0197B)
Water Balls
Wiggie Waggie
Wild West C.O.W.-Boys of Moo Mesa (ver EAB)
Wing Shooting Championship V2.00
Wonder League '96 (Korea)
Wonder League Star - Sok-Magicball Fighting (Korea)
Wonder Stick
Woodpecker (set 1)
WOW New Fantasia
WW2 Demo - Arcade Development Project [Homebrew]
Wyvern F-0
Zero Team USA (set 1, US, Fabtek license) [Coin inputs require holding down]
Zintrick / Oshidashi Zentrix (hack / bootleg) [Bootleg]
Zip & Zap [Imperfect GFXs, No Sound]
Zupapa!

(the same list for parents that ARE in mame2003 but not in FBAnext is over 1600, so i figure i want to just use FBAnext for its exclusive games)

of that list, I think it can be further narrowed to get rid of all the neo-geo, stuff that doesn’t work, and duff categories, so I’ll do that now and see if I can’t get a small list of the stuff that’s worth keeping in FBA.