I didn't my day play this game yesterday after watching a video by Mr. Fruit, and thoroughly enjoyed it. Currently, my city is making about $350-400 a day with over 1000 people. Currently, I'm sure I could just keep building with this configuration infinity, but I want a carrot.
A leader board system would add a bit of endgame through competitive play along with giving ideas to new players.
At that rate, challenge and speed runs would also be interesting to see.
Anyhow, keep it up, it's definitely doing well and a time sink for us procrastinators.