However, in the case of Out Of The Vortex, a side-scrolling fighter based on the comic book of the same name, nobody outside of the development studio Cryo Interactive knew it existed until very recently.
Cryo is a company famous for its bold FMV-based titles, such as Mega Race, Dragon Lore and Lost Eden, but it did, from time to time, dabble in licenced titles, including Timecop, Woody Woodpecker: Escape from Buzz Buzzard Park and Cheese Cat-Astrophe starring Speedy Gonzales. It also created the interactive movie Dune for Virgin Interactive.
As a fairly late-stage Genesis / Mega Drive release, Out of the Vortex was shaping up nicely, but with development around 95% complete, it was canned around September 1995.
You can read about its development – and its recent discovery – here. You can also download the prototype from the same site.