Hrm... I actually still use an old definition of 'casual game' , one that many "gamers" today frown on. And that is, to me, a casual game is a game that a large chunk of people play, the "must haves" for a system, if you will. If you have a system, the games that are in common agreement that people should have, are the casual games. Even in board games, the 'casual' ones are the ones that everyone "should" have, like Monopoly, Risk, etc. Clearly it's not a mindless matter.

And today's "casual" games by common (read: 3rd party) definition, I have to take those on a case-by-case basis. And I can't lie; quite a few of the Wii's 3rd party games I actually do call "half-hearted efforts."

Dead Space Exctraction is pretty good =)

I know how long they've been around and I never considered them games whether it was a text adventure in a book or on a screen. Call them interactive fiction or whatever but they're not games or videogames. Online poker isn't a videogame but it's still a game. Like poker, stories can be digitized. Just because you're pressing A to go to page 46, doesn't make it a videogame.

 Why ? Is it because these games required more thinking than button mashing?   Just because Civilization was first a board game  I don't see why this would  make Civ 5 less of a video game.

Chess has been branded by the videogame industry as "casual" as has a lot of other boardgame and cardgame stuff. And there is a degree of irony behind this also.

Anyhow, this being said, what is the opposite of "casual"?  People say "hardcore"?  That had meant games with bad interfaces that are not easy to get into and dedicated to fanatics.  Well, it had since gone on to mean, "games for the teen demographic with lots of sex and/or carnage" like Modern Warfare.

A good game, with universal appeal, is easy to get into, but has a lot of depth to it.  That is a sign of a good game.  It can be played, and enjoyed, on a lot of levels.

Ok, let me give you another definition of "casual" gaming.  These games are considered to have lower development costs, and broader appeal.  The opposite, with broad appeal, is consider also "hardcore" gaming and consists of games with monster development budget costs.  These games, on the whole, will bankrupt the videogame industry, if they keep thinking increased production costs are the magic bullet.

Civilization, the computer game, is not based on the boardgame "Civilization" which was published by Avalon Hill (and others) but the computer game "Empire" I believe.   It also has stong ties to Simcity, and Sid Meier actually had Simcity in mind when he was originally doing it ("Empire" became the shift that made it what it became).

And there is clearly a difference between interactive fiction and a game, although videogames tends to be a catch all for them. 

This is first I read Chess was casual. There are more books written on chess than any other game.  Since chess is one on one, two noobies can play each other because they both suck. Checkers or even Monoploy is a lot more casual than Chess.

 You can easily call Red Dead Redemption an interactive fiction.
 I do remember Empire yet I can see Sid Meier take some ideas especially tech age from the original board game. They finally did make a board game after the video game.

In my opinion, if the game is bad, it's for casuals. Case in point: Game Party.

It is tough to define casual games.  I would be more likely to point out a casual gamer.  One that plays a few select games, maybe quite a bit, but doesn't branch out or particularly want to be challenged.  Someone who mainly play sports games is a good example.  Also, someone who only likes to play FPS titles like COD or Halo.