Also, what kind of games do you enjoy playing the most and WHY?
I play mostly traditional pen/paper RPGs, specifically a modified version of D&D. Infrequently I play board games like Scrabble or Pictionary, just as a social activity. With the right group, these can be surprisingly entertaining.
Aside from entertainment reasons, what things (physical, mental, social etc) do you learn from gaming?
I don't exactly learn from RPGs, if anything it is more like skill development. I get to exercise my imagination and creativity in different ways, and try to understand how different kinds of people might see things in different situations. It need to think on my feet, make do with less than optimal solutions (after all, it's only a game!), and at least try to stay in character.
When I learned about type theory, I realized that all my RPG characters were basically my own type. After that I made a conscious effort to design characters with significant differences, but I then found I was much less successful and comfortable playing them. Gaming is one of the few activities I do with a group, so it is a significant social outlet as well.
How many hours per week do you estimate you spend playing?
My RPG group meets on average every other week. Add prep time/research, and it probably averages to 4 hrs/wk.