I was thinking along similar lines the other day. One of the things I realised was that imagination played a much bigger part in my enjoyment of games than it does now (as it did with playing with toy cars, lego etc. back at that age).

I vividly remember playing one of the Shinobi games on the Sega Master system, and spent a huge amount of time wandering back and forth in the levels thinking about the townsfolk who occupied various buildings and their work days.

There was also a mountain range in one of the backgrounds on one level, and I recall spending time planning to explore it later, even pausing the game to draw a map of an imagined village there.

Of course now the vocabulary of games (and my understanding of them) has changed a lot, and it's far more obvious what the limits of a game and its interactive areas are - to me they're now throwaway pieces of entertainment, no longer worlds to inhabit and explore.