well out of this world and flashback certainly aren't side scrolling shooting games, and it wasn't the graphics that were ground breaking it was the way the game played and the animation, basically the whole concept of them. they really aren't a lot like anything else thats been made before or since. the games are very well animated and you have to solve your way through a lot of the game, although there is action as well, but they certainly aren't your average mindlesss button pressers(not to knock those types of games though because i like them as well!). but for a good portion of the game you must rely on your own resoucrefulness and awarness of your surroundings and be able to use objects around you to make progress in the game. for example the opening stage you have no weapons and you are being stalked by a beast that you must out smart to get past. you don't find a weapon untill later in the game. here is a link you can find some more info at:
http://www.the-underdogs.org/game.php?id=2345