Having played video games my whole life, I find it funny what constitutes "hard core". Back in the day, games like Contra or Super Mario were main stream. RPG's and light gun games were for the hard core. Then there was a time where non-Street Fighter fighting games, or non Nintendo/ Sega systems were for the hard core. In the 32 bit era, games like Final Fantasy, Metal Gear, and Mario 64 were main stream. Games like Rez, DDR, and Vagrant Story were for the hard core.
Now, if a Contra game is released for the Wii, it'd be considered a game for the hard core. If a game that didn't have a big following in the 90's like Dance Dance Revolution (which was for the hard core back then) came out today, it would be another example of Nintendo going main stream.
Long story short, the definition of hardcore differs based on what the majority is playing. There is no set definition of hardcore games. It's just a term that more avid gamers use to build themselves up.
