Painkiller Overdose is the buggiest retail release I've played recently. It crashes consistently, especially if Firefox is using a bit of the 2GB of memory (the game doesn't require much).

The Battlefield series of games were notoriously buggy, but not so bad that people couldn't enjoy them. The basic stuff of shooting people tended to work when needed.

Lately, a lot of PC games that used to work no longer do. That's more the fault of changing targets for DirectX and graphics cards, as well as evolving PC hardware, breaking the older games. A fun example is the old Novalogic Delta Force games failing to run because a programmer made a dumb choice in streamlining a check for swap space.