The truth is, it's like a sport. There's fans, enthusiasts, commentary, amateurs, and pros. I'm probably forgetting a few categories.
A fan watches the games as they are played. An enthusiast follows the sport, knows strategy, the players, and things like that. The commentary is typically journalists. The amateurs play the sport and may be enthusiasts, but aren't good enough to be pros. The pros, are, well, the pros.
Games are like that. I consider myself a gaming "enthusiast." One of my roommates is also an enthusiast. My other roommate is a fan. He plays "non-games" mostly, but he's by no means "casual" at Wii sports tennis. CrimmJim, Jonnyboy, Windy, SvevEvan, and the rest are Commentary-enthusiast hybrids, some more commentary, some more enthusiasts. Hardcore are people involved with the MLG, or other competition. Like Starcrafters in South Korea. People who play competitively at more local levels (tourney-something-or-others, in smash bros.) would be the amateurs.
As you can see, even those five categories don't really cover everything. But hardcore/casual certainly doesn't cut it. Certainly.
I haven't listened to the podcast yet, though I will. I will.