Not really fun and very unfair
This game, a follow-up to Part III of Back to the Future, was developed by Probe Software and published by Arena Entertainment in 1991 for the Sega Genesis. The game was also released for the Sega Master System and various home computers. This game involves Marty McFly going to the old west and convincing Doc Brown, who has been living there for 6 months to come back to the future. At least this version actually represents the film way better than the NES version.
Despite being a big step-up going over to a 16-bit console, the graphics on the title screen and the introduction cutscene are fugly and have horrendous color palettes. For some reason, the Genesis version is also darker than the other versions of the game, due to the color palette definition error. In addition the title screen music is actually from the film but it's godawfully terrible, sounding heavily distorted and hardly resembling the actual theme of the Back to the Future franchise.
With stiff controls, there are only four stages in the whole game (three in the Master System version).
The first level has you riding a horse while avoiding various obstacles and enemies. This level is ridiculously hard due to the speed of the gameplay, making it impossible to react in time to obstacles or enemies, and there's so little room for error, that even in tool-assisted speedruns the player can just barely complete the level. James Rolfe (AVGN) said it was a "perfect example of a game that starts out way too hard" and that he "guess they were too lazy to design a longer game, so they just made it more difficult so it'd take longer to beat, that's all!", and in his Back to the Future ReRevisted AVGN video, it was the only part of the game he played before giving up and throwing the cartridge on the floor. The level is easier in the other versions of the game due to less speed present in these versions. The music in the actual levels aren't any better, the most annoying being what sounds like Ghost Riders In The Sky (during this stage).
Clara's tombstone that appears if you fail the first stage has her death year as "1855", instead of "1885".
The second stage is a mediocre shooting gallery.
The third stage has you throwing plates at bad guys with strange hit detection.
The fourth and final stage is on the train with odd platforming. If you die, you are towed back to the beginning of the stage, making it a problem due to the short time limit.
The ending is just a picture of the DeLorean with a few scrolling sentences of text.
Overall, an unfair and boring game.