I'm sure about 99% of active users of GameSpot have all noticed the frequent use of the terms "hardcore gamer" and "casual gamer". However, it seems that everywhere these terms are used they are used to refer to different concepts. Is a hardcore gamer an FPS gamer, or is it a Miyamoto gamer? Is it hardcore to play games thoroughly or is it to play certain genres of games? Is a Wii owner automatically casual and a 360 owner hardcore? And is a person that plays a game like Picross DS dedicately every single day still a casual gamer?
My personal view on the subject is as follows. A hardcore gamer is a gamer that plays games of any type, genre, age group, or target audience, on any console/PC, and does so dedicately. Be it playing Gears of War 'till 4:00am or Brain Age an hour a day, any gamer that plays a game in such a way as to get the most out of it is hardcore, or how I like to call it, "dedicated".
A casual gamer, on the other hand, is someone that picks up any game of any type, genre, age group, or target audience for any console/PC and plays it superficially, meaning that they don't care to go beneath the surface of the game. Whether it be playing Halo 3 because "it's cool" or playing Flash Focus just to kill some time, any gamer that plays a game to get what is immediately available from it, instead of going bellow the surface, is a casual gamer.
In other words, what type of gamer we are is not determined by the game we play or the console we play it in, but by the way we play. If you take games seriously, whether they be like BioShock or like Rayman Raving Rabbids, you are a hardcore gamer. If you take games as a good timekiller, whether they be The Orange Box or Big Brain Academy, then you are a casual gamer.
I believe these are the best definitions of what hardcore and casual mean. Just think about it, if you're reading this right now, it means you care enough about games to not only visit a site like GameSpot but to also read through its community's blogs. And yet, some who read this own a Wii, and others a 360, and even others a PS3 or a PC. And within those consoles, people play different games of different genres, age groups, and target audiences. Thus, we are hardcore because of the way we play and care about games. It is this principle which defines the line between casual and hardcore, nothing more, nothing less.