I know the round table is over, but Ghosts in the Game snuck in a last-minute post that I really want to respond to.
You might remember my own post on the matter, which says that home is created by having the rest of the game orbit the home. Leave the home, return to the home, leave the home, return to the home. Physically (gameplay), socially, and/or emotionally.
Now, I'd like to explain why Evil Genius and Dungeon Keeper 2 accomplished this but the Sims didn't and, say, Starcraft didn't. I really did like all of these games for some definition of "like", but we're discussing only the sense of home they provide - or fail to provide.
Evil Genius and ilk essentially allow you to build a base to defend from whatever onslaught the enemy has in their plans. Both the Sims and Starcraft allow you to also build a "base" - but these bases don't feel like home at all, whereas Evil Genuis' style lairs tend to. Why?
Duncan says it's because the bases are defensive rather than either offensive or nothing-fensive.
I'm going to explain it in terms of my "orbit something long enough and it becomes your home" theory.
In the Sims, there is no orbiting. You are grounded. You are glued to the house. You cannot leave it. The Sims 2 recognized that this might be trouble, but its adventures to the mall or whatever didn't cut it. This is because, when you leave your home, it should be emotionally, socially, and physically - or at least two of the three. The Sims never varies at all in gameplay: the physical gameplay you get at a mall isn't any different than the stuff you get at home. Socially and emotionally, the variations are excruciatingly minor and pointless. So, you never really orbit anything in either Sims.
However, in Evil Genius and Dungeon Keeper 2, you have extensive orbiting. Most of the game is spent trying to get home. Every time you beat a level, you have to start over, building back towards that ideal state you hold in your mind. The physical and emotional play of the game vary hugely as each level progresses.
The assault at the end of each level is not actually the primary joy of these games. It is simply an anchor to give you a distinct feeling of what home should be. It directs you towards making a certain kind of home: a kind of home which you'll repeatedly refine and get closer to in each map. But that home isn't "home": it's the act of creating that home which is "home".
The idea is genius, and a perfect example of how to include home in a game without making it all fuzzy-wussy. Every level, you leave home and spend most of the rest of the level struggling to return to it... all without realizing that you are home, during the act of struggling to return to it.
Now, in Starcraft and similar games, you get a very different feeling - even though there's the same "rinse and repeat" cycle. Some very experienced (or dull) players will feel the same feeling of home when they build a specific layout of base that they know is best, but most players will never feel that. Why?
There's no orbiting. Remember: physical, emotional, social. There are differences between early game and endgame in Starcraft: emotional, physical, and social differences. But they are the difference between having fifty of something and having sixty of something.
In Dungeon Keeper 2, it's the difference between having negative fifty of something and fifty of something.
There's a smaller max, but it isn't the max that matters: it's the distance you travel. In Starcraft, you travel from tense to very tense and back to tense. In Dungeon Keeper 2 and Evil Genius, you travel from Laid Back to Amused to Tense to Amused to Very Tense and back to Laid Back. You constantly travel away from your home state of "building a home", and constantly travel back.
In this case, it's not the thing you've constructed that feels like home: it's the act of constructing it. You constantly return to that focus, and the emotional, social, and game-rule physical differences between that and the assault at the end of the level are immense.
I hope this is clear. And, Duncan, thanks for the insight. :)