A gamer is a person who is good at certain types of games, mainly those that require a bit of skill or patience to be good at. For example you can call yourself a gamer if you have a max level wow character of if you can do a 360 headshot in mw2 however you can not refer to yourself as such for playing casual or just plain stupid games.
Thus calling yourself a gamer just means that you consider yourself sufficiently "pro" at any number of games that you can impress other people by playing.
Also there is no difference between gamer and hardcore-gamer, the correct term for a "gamer" that isn't that much into video-games is "casual gamer".
As for valid and constructive arguments to support my theory:
1. I am Batman.
2. Batman is ALWAYS right.
3. Therefore my thesis is correct
Thus calling yourself a gamer just means that you consider yourself sufficiently "pro" at any number of games that you can impress other people by playing.
Also there is no difference between gamer and hardcore-gamer, the correct term for a "gamer" that isn't that much into video-games is "casual gamer".
As for valid and constructive arguments to support my theory:
1. I am Batman.
2. Batman is ALWAYS right.
3. Therefore my thesis is correct