I realized that some video games appeal to me because of their mechanics. Starting with scarce resources and poor (or lack thereof) base of operations, putting those back in shape has a strange satisfaction associated with it, like finishing a puzzle or tidying up the room.
The games are designed to be challenging, but not too hard or mundane like chores in real life (else it would not be logical for the players to invest their time). Add in some variety, random surprises, and cute girls to lure players, you have a perfectly enjoyable game.
Designing a reasonable model of monetizing, with occasional events and advertisement, and it might be the next block buster social game.