The Sims 2. The 2004 sequel shipped at least 20 million copies across all platforms, and its 8 expansion packs didn't do too bad themselves. Maxis' life sim definitely can't be accused of living its own life unproductively.
The good news is that EA is doing a solid by its players, apparently. The publisher says it's offering Origin-registered owners a free copy of the most-up-to-date version, The Ultimate Collection, which will appear in Origin in the next few days before support ends on July 22. Not only is it the latest version, but The Ultimate Collection also includes all the expansions and stuff packs, and players are able to transfer their save files across.
EA says anyone who has "purchased and registered a digital copy of The Sims 2 on Origin will receive the Ultimate Collection." By the looks of it, registering the game on Origin isn't straightforward as you'll have to contact an EA Game Advisor, but it's probably worth it to lock some poor Sim in a toilet-less room with every single tool at your disposal.