Big Brother, probably because it was one of the first ones i played. But nowadays there are just too many great games: Timestamps, Milfy City, Photo Hunt, ...
i wouldn't be able to choose just one.
Of games not previously listed, I'm really enjoying Ravenous. The story is good and the models are very nice. Also a shout out to Evermore, for the same reasons.
Hearth Problems - The little sister is a pretty little slut
Ohh daddy - Pigtails are my Achilles heel
Desert Stalker - the daugthers are so fucking hot
Family Faring - well u know