Agreed! Also, it's used to belittle those who play games like Bejeweled or The Sims. How can we argue with the fact that The Sims sold more copies than God of War? Why, by insisting that The Sims is for casual people who don't know anything, of course! 

In fact, I've seen many people use many different definitions in order to suit their own purposes. Whatever games/platform they like -- that's hardcore. If you don't like their games, then you're not hardcore, and your opinion isn't as valuable.  

By this definition, professional CS players aren't hardcore gamers. That's silly, in my opinion. You're welcome to define this however you'd personally like, as this is just slang and not a technically recognized term, but I think reasonable people (including me) can disagree with it.