When I was really young, in the arcades I played on my own.  When I was at my parents' trailer, they had a game room with a stand-up Kangaroo (woot!) and a Pac-Man cocktail (woot!).  I liked to play them with friends, but found I had none.  (Heh. Actually, most of the time, my friends weren't up at the same time I was.)  When I got older, I played Coleco-Vision mostly alone, as my sister was 3 years younger and my brother was 4 years younger.  It was either alone, or else, play "Lady Bug" and listen to them cry when they lost.  Older still, I played Wolfenstein and Doom alone (obviously) and then got into games like Command & Conquer.  Buddies of mine all brought our comps (with 15" CRTs) loaded into our cars to a cottage and played head-to-head for about 18 hours straight one day.  (AWESOME!)  Then, I got into FPS like Duke Nukem (alone) and Counter-Strike (net play) on the PC, but never quite got into console games or the like.
When I finally build my cab, it's going to be placed in my kids' toyroom (they're 9 and 3, respectively, and more importantly, both BOYS - woot!) and we're going to play them all together, I'm sure.  I'll be making certain to have the best of the best available - Pac Man, Galaxians, etc. - so that they get the feel for what real gaming is about.