Any recommendations for the best motherboard for...

Depends on your budget. A proper graphics card from ATI or nVIDIA are better for games, but for things like the SIMS you could get decent performance from onboard graphics. It really depends on what your budget is.

Boards from ASUS, Foxconn and MSI are usually good enough. Coupled with a low end dual core processor they can be good enough for games like the SIMS.