There are "casuals" amongst the userbase of all 3 consoles.
A "casual" is just someone who buys few full price games a year. Read above.
This whole mythical notion of the "core" gamer being someone who must play only FPS - and a casual plays only Angry Birds is false. There are casuals who buy 2 - 3 JRPGs a year and put a few hours in each week. There are casuals who buy Dark Souls and play it for 2 weeks in the holidays. There are core gamers who go out and buy 3 new games and play Stickman BMX on the bus. There is no elite - just attach rates.
Once again - read above.