It's SimCity. It's a brand name that has the potential to sell millions, though of course it doesn't mean it has.
It's a brand name that hasn't been around in awhile and it's a different market these days. I'll reserve judgment on sales figures for awhile.
Well, so was Diablo. Though in all seriousness there were some ARPGs between D2 and D3 and really nothing like SimCity between SC4 and 5. The Anno series is an economic chain game, it isn't an evolving city game like SC. The only game close to SC that was released in the meantime was CitiesXL but that was a terrible game.