Um hell no, my mom tried hard as hell at tetris but that sure as hell did not make her a hc gamer.

Going by your argument, someone may play Zelda:  Twilight Princess casually but play Animal Crossing:  City Folk hardcore (that's me, by the way).  I couldn't agree more.

Why not?

can we use the term "serious gamer" instead of something that sounds like a bad porn?

Nope, we're men!

Manly, sexually driven men!

just sounds kinda sexually insecure to me >.>;

This....

So time and effort put into a certain game defines how casual or hardcore it is...

I don't personally use those terms because I don't care about how people classify the games I play. As long as they're fun I will play them but if I were to use them, this is probably the definition I'd think about.

I don't think how much time an individual puts into a game defines the game, but rather the gamer.

And I don't use casual or hardcore to define games anyway, like lolita. I will use niche though, which i think is how most people use hardcore.

oh god, you actually thought he was serious.....

Why not?  My Dad is absolutely a hard core gamer.  Plays more than I have time to.  Plays CoD, Halo, Mass Effect, Fallout 3,......

The fact he sucks at them all, does not change that he's a hardcore gamer.