To me, it seemed like NEC Avenue, was better at making original games, rather then ports. That's what always stuck out in my mind.
Oh, as for a list of unreleased games, though I don't have a bunch of concrete sources for this list, this is what I've come up with, from various lists over the years, some were listed in old NEC & TTI flyers, like Arena 3000(or maybe it was 5000) that I can't even find anymore, but, I kept track of the games. One I've always been obsessed with, is Riftwar Saga, which has like 3 pictures from an old EGM. Anyways, here's the list I've compiled:
Alien vs. Predator-Action-card/cd?-TTI
Alien 3-Action-card/cd?-TTI
Arcade Card Duo
Arcade Card Pro
Arena 3000-sports?-card?-Icom
Art of Fighting-Fighting-acd-TTI
Astralius-RPG-cd-IGS
A Train 3-Train Mangament-scd-TTI
Baby Jo-Action/Crap-scd-TTI(boy, I can see the people lining up for this one!)
Barunba-Shooter-NEC
Battle Load Runner-Action-TTI
Black Hole Assault-Fighting-scd-TTI
Blood Gear-Action/RPG-scd-TTI
Bonk's Quest aka RPC Genjin-RPG-TTI
Camp California/Yo Bro-Sports Events-card/cd?-TTI(same game as Camp California.....or Yo Bro'?)
Champion's Boxing(Forever?)-Boxing-TTI
Cosmic Fantasy-RPG-cd-Working Designs(was going to be released at a lower price point)
Cosmic Fantasy 3-RPG-scd-Working Designs
Cybertwins-Action-cd-Working Designs(TTI then grabbed the rights to it, & was going to call it Shockman 2, with Working Designs supplying the voice acting)
Dangerous Dimensions(Journey)RPG--scd-TTI(?)(I have pics of it)
Die Hard-Action-TTI-I don't know if it was just the PC Engine game, or a brand new game
Discis Books-Kids-scd-TTI
Double Dragon 2-Fighting-scd-TTI
Download 2-Shooter-cd-TTI
Castlevania X-Adventure-scd-TTI
Dragon's Lair-Strategy-scd-TTI(I have know idea, if this even hit any production)
Dragon Slayer: Legend of Heroes 2-RPG-scd-TTI
Dynasty Wars-Action-scd-TTI
Exile 3-Action/RPG-scd?-Working Designs(only in the talking stage, I doubt it ever got any development)
Fantasy Star Soldier-Shooter-scd-TTI
Fatal Fury 2-Fighting-acd-TTI
Fatal Fury Special-Fighting-acd-TTI
Far East of Eden 2-RPG-scd-TTI
Final Soldier-Shooter-TTI
F-1 Circus-Racing-TTI
Gain Ground SX-Action/Strategy-scd-TTI
Gao-card/cd?-TTI
Gekisya Boy(Photograph Boy maybe?)-card/cd-TTI
Genocide-Action-scd-TTI
Gradius-Shooter-Konami
Gradius 2-Shooter-TTI
Horror Story-Action-scd-TTI
Human Sports Festival-Tennis/Soccer/Golf-scd-TTI
Image Fight 2-Shooter-scd-TTI
Jim Power-Action-scd-TTI(Wooh, another award winner, better then Baby Jo, good music)
Keith Courage 2-Action-NEC(nothing ever came of this game but I do have a Turbo Play where they claim it was in production, might've been refering to Granzort, which is a completely different anime the Wataru)
King of the Monsters 2-Fighting-acd(originally a scd)-Working Designs
Lady Phantom-Strategy-scd-TTI
Macross 2036-Shooter-scd-TTI(finished, but had some glitches in it, but will we ever find a translated version of it, someday I hope)
Macross Eternal Love Song-War Sim-scd-TTI
Mad Stalker-Fighting-acd-TTI(what Genocide should have been!)
Marble Madness-Action/Strategy-Tengen
Millitary Madness 2-Strategy-scd-TTI
Mystic Formula-Action-scd-TTI
Neutopia 3-RPG-cartridge/cd?-TTI
Nexzar-Shooter-scd-TTI
Ninja Warriors-Action-TTI
Parodius-Shooter-Konami
Paradroid-Shooter(?)-TTI/NEC?
Peter Packrat-puzzle-card-Tengen
Photograph Boy-action-TTI
Pit Fighter-Fighting-cd-Tengen
Populous-Sim-cd-NEC
Power Gold 2-Golf-scd-TTI
Power Tennis-Tennis-TTI
Predator-Action-card/cd?-TTI
Psychic Storm-Shooter-scd-TTI
Ranma 1/2-Fighting-scd-TTI
Rastan Saga 2-Action-NEC
Rayxanber 3-Shooter-scd-TTI
RBI Baseball 3-Baseball-Tengen
Record of Lodoss War-RPG-cd-TTI
Riftwar Saga-Action/Adventure/RPG(?)Kid's Creation(or something like that, I have 2 or 3 pics of the game)
R-Type Complete-Shooter-scd-TTI
Salamander-Shooter-Konami
SCI-Action/Racing-NEC
Sherlock Holmes 3-Digital Comic/Strategy-scd-TTI(my friend Bill's dad worked at Icom & he told me about some of the filming being done for this project)
Snatcher-Digital Comic-scd-Konami or TTI(I can't remember)
Spriggan-Shooter-cd-NEC/TTI/Working Designs all attempted to release it
Street Fighter 2(aka Fighting Street 2)-Fighting-TTI
Strider-Action-acd-TTI
Super World War-Strategy-cd-NEC
Super Darius-Shooter-cd-TTI
Super Darius 2-Shooter-scd-TTI
Super Swarzchild-War Sim-scd-TTI
Tecmo World Cup-Soccer-scd-TTI
Tennis Cup(Davis Cup?)-Tennis-TTI
Terminator-Action?-card/cd?-TTI
TV Sports Baseball-Baseball-NEC/TTI
TV Sports Boxing-Boxing-NEC
TV Sports Series-Football/Basketball/Hockey/Baseball-scd-TTI
Twin Bee-Shooter-Konami
Wizardry 1 & 2-RPG-cd-TTI
World Class Baseball 2(Power League 4)-Baseball-TTI
World Heroes-scd-Fighting-Working Designs
World Heroes 2-Fighting-acd-TTI
Xak 1 & 2-RPG-scd-TTI
Ys 4: The Dawn of Ys-scd-TTI
On the games based on movies, I can't remember if it was NEC, or TTI, but I'm inclined to say TTI. It was in an old EGM of mine, that would take forever to find.
There were also some unanounced Disney games in the works supposedly
Also, there were several fighting games in the works for card, cd, & scd according to an old Turbo Play
I'm sure there's a grip more, that I just couldn't find any info on. Someday, I will find all the old letters I got from NEC, & TTI(before I met my friend that worked their).
You can ask me about any of these games, & I'll tell you what I know......if anything. I also have a load of pics up(on the Hudson boards) for some of these from old mag's.