One of my guilty pleasures is Football Manager (and previously Championship Manager), it is definitely my favourite type of game - open-ended, considered, and graphics are not the most important part - it is gameplay.
On the SI Games website there is a forum with a programmers corner. There is a great little post on the forum by Marc Vaughan (lead developer type guy) about designing a management game. It covers in quite a lot of depth, although it is not completely finished.
