I'm probably late to this party, but I recently discovered Jason Rohner's "game" Passage and I must say that it's a brilliant piece of work.
A metaphor for adult life, the player walks a 16-bit character (which reminded me of the Activision's Pitfall Harry) on a "life journey" - the first session I played, I walked straight ahead - got a wife (more on that in a second) and scored moderately high points-wise but encountered no treasure (which increases points) and no obstructions either. As I walked along, the area ahead of me (the future) was hazy and as the character aged, the future became clear but the past grew hazy. (It reminded me of a trip I had once when on 'shrooms, but that's a story for another time.) If you "go off the straight and narrow" you encounter treasure chests which can be full or (more often) contain nothing at all.
There are also obstacles which can be circumnavigated alone, but if you have a wife following you, there are many paths you cannot take - as a married man, I can tell you this was the most poignant aspect of the design - a mechanic never really done in games outside of Ico - and one that really brought home the whole theme of the game for me. I would love to see this design idea (caring for someone else) brought to more games - I'm beginning to feel that the era of the solitary hero against the world in games is almost dead.
I highly suggest everyone to experience Passage for yourself here.