Its not really as black and white as the 2 terms make it out. I suppose for me there is an element of what you mentioned, a hardcore game does have to appear as thought the developer has put some effort into the game. But I'm not sure I agree that a hardcore game always has to be difficult. For instance, I would count the latest Prince of Persia as a hardcore game, but due to the instant death/revive mechanic the developer put in, it makes the game appear easy and less of a challenge.
I think for me, a hardcore game is very similar to a mature game, which deals with more serious situations, or a game where more thought has to go into it before you can really start to enjoy it. This could be in developing strategy, solving a complicated puzzle or having to seriously think about the outcomes of your actions. Its a game which isn't just "pick up and play" although that doesn't discount games which can have an element of this.
The ideal scenario is a game which can transcend both realms which is something that Nintendo manage to do very well, having both hardcore and casual elements to create something that is both. Another example would be GTA, a game which you can spend hours on, getting into the story, completing all the missions, or just play for a little while, causing mayhem and carnage.








