I've had Dear Esther on Steam for years and I was planning on playing it one day or the other. Glad I can cross something off my list.
That said, overall I agree on your definition of game, although this is a pretty sticky issue. As you notice yourself, before the advent of videogames games could be both children toys or sports, so it's a word that encompasses a variety of stimuli and circumstances, and the interaction element, in the real world, wasn't really up for discussion. So yeah, I get and, again, agree with your definition, but I would understand if someone where to say "no way, even walking around a virtual world could be classified as gaming, as long as that's what you feel you're doing with your time" because, basically, we're learning and establishing stuff as we go forward.