Warp Zoned writes:
Walk over to your media shelf and pick up a copy of Wii Sports or Halo 3 or Call of Duty: Modern Warfare 3. Odds are at least one of these titles will be in your collection. What do you call the item in your hand? Some people consider these titles “interactive entertainment,” but most of us just call them “video games.” Or are they “videogames?” Though they’ve existed for over forty years, no one has ever answered the question “video game or videogame?”
Language evolves, it always has. Fifty years ago you'd be punished for ending a sentence on a preposition, now can put "txtspk" into an exam and pass so long as what you've written is understandable.
As for video game or videogame, I'd go with the former because the definition stands alone as two words. That's personal choice though and it wouldn't surprise me to see the latter become the norm as the hobby becomes more popular.