Sims doesn't count, as it's not really a game. It's playing house.
My vote goes for Too Human, and I only played the demo. I'm sure there's some horrendous sports game out there that's worse, and we really shouldn't count shovelware, but Too Human was so bad I would turn off the TV and pick up a book whenever someone else entered the room. I was too embarassed to play the demo for a few hours.
I don't understand the Farcry hate. I loved that game, it was like going on safari. For humans. Maybe everyone was expecting a heavily scripted Blood Diamond knockoff, but as bad as the first game's story was, I'm glad they opted to not have one. The AI wasn't deadly effective, but they were realistic. Guys would work in teams to flush you out of the bushes, and run from the fight when injured, sometimes stealing your vehicle. I guess it depends which you value more in a game: story or gameplay. Although that game did have a massive glitch that corrupts ALL your savefiles. And only happens once you've done more than 80%. So that's a good reason not to play.
And anybody that says Fallout is trolling.