A hardcore game is some thing that is mostly defined by personal preference. I think it's a game that has a decent learning curve to it, making the experience more involving for the gamers.

EDIT:

BrainBoxLtd said:

 ...

Pink watermelon? 

Hardcore videogamers = videogamers who take videogaming seriously, sometimes they take one system more serious than another, we call those fanboys.

Edit: Anything a devoted gamer loves to play can be considered hardcore, hardcore games don't exist in my opinion. It's either fun to play or not fun to play. The only real distinction I see is good or bad games but that's just my opinion. 

I don't know how other people use it, but to me, a hardcore game has two parts:

1) you will not know how to beat it right away

2) even after you understand how to beat it, it is still challenging enough that you may not be able to beat it.

Right now Mario Galaxy is slowly developing into a "hardcore" game as I hit the later levels. Some of those levels are downright nasty.

Phantom Hourglasss was NOT a hardcore game for me

 Thats all well and good but it doesn't help define what a hardcore game is.

Vertigo-X said: BrainBoxLtd said: Pink watermelon?

Violet watermelon

Ultimately its difficult to define what a hardcore game is. However, you tend to recognise one when you see it. For example, the moment I played Ninja Gaiden on the Xbox I knew it was a hardcore game, because casual gamers simply wouldn't get a lot out of it.

 Most popular games are either casual or offer a bit of cross-over between hardcore/casual. Games like the Mario platformers and Halo are fine examples of this. They appeal to a casual audience, which explains why sales are so high, but at the same time appeal to some hardcore gamers through getting 120 stars or beating the game on the Legendary difficulty.

I would imagine the number of games that are purely hardcore to be quite low. Far lower than the number of games that are purely casual.

After all the discussion here, this now seems appropriate:

gamers who don't scream at the top of their lung that they are hardcore gamers, or accusing other of being casual gamers, and can figure out how to successfully operate a game system and learn how to play a game by either reading manual, in-game tutorial, or figure it out on their own without excessive cussing. In addition, their first choice of entertainment/relaxation/etc is video game.



Also, they spend more time playing games compare to other activities without soiling themselves (or at least seems like they soiled themselves).





What?

Hardcore games are first-person shooters like Halo and Killzone!

 If you have to ask, you're not hardcore. I know I'm not, purple isn't my color. =P

@picko: see my edited reply. Also we could draw the line and say games that take themself serious are hardcore games.

Games that require more than just luck to advance... any game that require a certain amount of skills can be considered hardcore regardless of the genre.