Honestly I think that's a bit of a stereotype of the gaming industry.
At the moment I'm playing LIMBO, a black and white puzzle platformer set in purgatory where you play a boy with dazzling eyes searching for his sister, complete with spiders, brain worms, machinery and incessantly creepy use of gore.
My current favourite multiplayer first person shooter (The action comedy genre of gaming) is Team Fortress 2, a truly team based multiplayer slugfest which is like an interactive Norman Rockwell piece complete with bionic hands, drunken Scotsmen, jars of urine, psychotic ex-SS physicians and Sandviches (OM NOM NOM!).
The most successful and widely recognised gaming franchise of all time involves a fatass Italian plumber ingesting mushrooms and flowers to jump on turtles in a place called the mushroom kingdom so he can rescue his princess girlfriend from the clutches of a fire breathing turtle.
Science fictioney type games, while there certainly are alot of them I find that most of the bigger titles go at it from a unique angle, Halo is a sci-fi first person shooter which displays the aliens from a fanatically religious standpoint, Mass Effect is a third person action rpg which explores the concept of space diplomacy and the human race's acceptance with alien species, starcraft 2 is an RTS which simply basks in science fiction badassery and polishing it to a T being set in a warring universe of overcompensatory power armour and mass hordes of bloodthirsty 8 foot tall beasts.