Since half the point of having my own fucking world is that I don't have to deal with everyone else, I really truly hate the idea of mandatory multiplayer in principle. I do not want to need to be online, because the time I will most want to play your game is when my internet goes out.
I do not want a real challenge, because if it was a real fucking challenge I'd be too busy fighting to survive to achieve my ridiculous objective. game-runner, I want to pick a somewhat ridiculous objective and achieve it without the pressure of being told I suck because you idiots didn't figure out a way to score my ridiculous ambition.
Note 'game.' I do not want a campaign, objectives (my least favorite thing about Railroad Tycoon II and 3 was that it took me a good 20-30 minutes to figure out how to just play the damn game without any fucking objectives), or even scoring.
What I want in a City sim (or almost any other game) is a detailed simulated single-player game. I have never played a multiplayer game in my life unless forced to do so by the game's design.