1st worst: Uru, ages beyond Myst. Excelent graphics, but it doesn't have the atmosphere that the original Myst and Riven had.
2nd worst: The Sims - who wants to play "house" all day on a computer
3rd worst: MOHAA Warchest Edition. Lovely game at first, I couldn't stop playing it. Once I got into the expansions, however, I began to get bored with the same old stuff and eventually quit playing it.