You mean the clusterfuck that's sold over a million copies so far, a mere two weeks after launch?
Also, the current game is not being sold on it's own merit. If we'd never heard of SimCity before this game would not have sold 1M copies. It's because the nostalgia that many people have had playing the different city games from the mid '90s that's carried the current game so far.
I faintly recall other games selling multiple times that on launch.
1 million is very good, but not record-breaking. 1 million is very, very good if you consider SimCity and city-building games somewhat niche compared to games like Battlefield.