To me:
Hardcore gamer = a polite word for gaming nerd; even though it is kind of nerdy in itself. I wouldn't keep a straight face of some homely looking person yelled out to me "I'm a hardcore gamer!" I see the people who identify themselves as "hardcore" anything as being pretentious.
Casual gamer = a gamer who has more things going on in their lives than gaming and dungeons of dragons.
To the more nerdy crowd:
Hardcore gamer = The new cool word for 1337! It is a dignified title.
Casuals = Retards
I describe myself as a little dose of toxic masculinity.