Everyone defines it differently, and every generation has a different definition. What is hardcore to you?
BACK IN MY DAY, a first person shooter was casual. Real time strategies were casual. In the early 90's when these games began to appear, older gamers complained that PC gaming was being overrun by brainless teens who didn't care about depth and logic in games, but only simplistic shooting and dodging.
Hardcore was playing MS flight simulator in real time and doing the 6 hour trip from LA to New York in a 747.
Or playing those old submarine sims where you just stare at a CGA sonar plot for 3 hours waiting for something to show up, and when it does it's just an interference pattern you have to look up in the manual to see what the hell it actually is.
Really hardcore was playing the text based Hitchhikers guide to the galaxy and dying near the end because you didn't type in "Remove cheese sandwich from dog's mouth" at the start of the game, allowing the dog to swallow the entire race of evil beings due to an unfortunate sense of scale.
