Details are scant at the moment, Konami only announced the first six games to be included on the mini device:
- R-Type
- Ys Book I & II
- New Adventure Island
- Ninja Spirit
- Alien Crush
- Dungeon Explorer
Price, release date, and additional games will be announced at a later time.
https://kotaku.com/konami-announces-the-turbografx-16-mini-1...
Edit (7/12/19): Full list of games. 50 games totals, split between US/JPN ROMs:
US:
Alien Crush
Blazing Lasers
Bomberman '93
Bonk's Revenge
Cadash
Chew-Man-Fu
Dungeon Explorer
J.J. & Jeff
Lords of Thunder
Military Madness
Moto Roader
Neutopia
Neutopia II
New Adventure Island
Ninja Spirit
Parasol Stars
Power Golf
R-Type
Soldier Blade
Space Harrier
Victory Run
Ys Book I & II
JP:
Akumajo Dracula X Chi No Rondo (Castlevania: Rondo Of Blood)
Aldynes
Appare! Gateball
Bomberman ‘94
Bomberman Panic Bomber
Cho Aniki
Daimakaimura (Ghouls ‘N’ Ghosts)
Dungeon Explorer
Fantasy Zone
Ginga Fukei Densetsu Sapphire
Gradius (Nemesis)
Gradius II – Gofer No Yabo (Nemesis II)
Jaseiken Necromancer
Nectaris (Military Madness)
Neutopia
Neutopia II
Ninja Ryukenden (Ninja Gaiden)
PC-Genjin (Bonk's Adventure)
Salamander
Snatcher
Star Parodier (Fantasy Star Soldier)
Super Darius
Super Momotaro Dentetsu II
Super Star Soldier
The Kung Fu (China Warrior)
Ys I & II