As time goes on, unreleased games are found.  These retro titles could be complete though not released, betas, alphas, promo vids of gameplay, etc.  We have collected the coverage of these types of games here for your convenience.

Nintendo Game Boy Advance:
Overstorm (2D Action/Adventure)

Nintendo NES:
Chuck Yeager’s Fighter Combat (Flight Sim)
Sunman/Superman (Action)

Nintendo Virtual Boy:
Bound High

Sega Dreamcast:
ToeJam & Earl 3 (Action/Adventure)

Sega Genesis:
Beastball (Sports)
Beanball Benny (Action) Youtube
Frog Dude (Action)
Lobo (Fighting) Youtube
Stone Protectors (Action)
Time Trax (Action)
X-Women (Action) Youtube

Sega Saturn:
Atomic Runner/Chelnov (Arcade)

Sony Playstation:
Jet Moto 2124 (Racing)