You might assume that the allure of retro gaming is a modern thing, but even back in the days of 16-bit machines players were keen to sample titles from the past. To fill that demand publishers released reboots of classic titles; Activision's update of Pitfall is perhaps the most famous of the period, but we very nearly got a new version of the 1982 Atari 2600 shooter River Raid, too.
River Raid: The Mission of No Return - which is technically the third game in the series, following 1988's River Raid II - was shown off at the Summer CES in 1991, and several screenshots made their way into magazines of the era. However, the game was canned along with another retro reboot, Kaboom: The Mad Bomber Returns. According to Videogames Magazine - a clipping from which can be seen below - both of these games were held back to see how the aforementioned Pitfall update performed commercially, and they ultimately remained unreleased.
The original River Raid was notable for being created by Carol Shaw, who is widely credited as being the first female game designer thanks to her work at Atari in the late '70s. She would join Activision in 1982 and retired early in 1990, crediting the success of River Raid as one of the key reasons for her being able to do so. The title sold over a million units on the Atari 2600 alone, and was later ported to other consoles and home computer systems. Shaw had no involvement with River Raid II or the unreleased SNES game.
The source code for River Raid: The Mission of No Return was discovered in 2001, so there's a chance we might yet get to play this unreleased title.