On the Mega Drive/Genesis, Game Gear and Sega Master System a side scrolling platformer action game titled Jurassic Park was developed by BlueSky Software.
This game can be played in two modes, either as Dr. Alan Grant or as a Velociraptor. Playing as each provides the user with an alternative story and level design. The climax of the game mirrored the unused climax of the film, in which Grant must defeat a pair of Velociraptors by causing the Tyrannosaurus rex skeleton in the Visitors Center to collapse on top of them. Grant himself is the final boss in the same location for the raptor storyline: your dinosaur character must cause the bone structure to collapse via specifically placed kicks to cause Grant to flee. A sequel was released using a new game engine and new artwork (with some of the original art as well), entitled Jurassic Park: Rampage Edition. In it, Grant's helicopter (that he just escaped on in the first game) crashes. Now he must deal not only with dinosaurs, but InGen as well. A new raptor must also make it off the island.
The Sega Master System and Game Gear versions of the game differed greatly from the Sega Mega Drive/Genesis version, containing driving sequences using a jeep, and did not have the raptor choosable as a player character, only Grant. While the game was still a side-scrolling, platforming game, it was a completely different game from the Sega Genesis/Mega Drive.
Source: Wikipedia, "Jurassic Park video games", available under the CC-BY-SA License.