Living room. We had a pretty big house, but my parents would never allow more than one TV in the house (or cable, or a TV with a remote control. Eventually we got VCR. And a computer, after my dad needed to have one at home for work.) Eventually we got the attic finished, and a new model TV up there, but I was pretty much on my way out by then.
Anyway, in my game days, there was one armchair close enough to the TV for playing Nintendo. Since I was older, I usually took that while my brother sat on the floor.