I'll have to join the chorus of WA.
Generations doesn't do anything but add a couple of traits (Nurturing and Rebellious), one new profession (Daycare), and introduces the irritants known as Imaginary Friends and Over the Top Punishments.
Late Night introduces Mixology as a new skill, hot tubs, and the ever annoying Vampires and Paparazzi.
Showtime adds three new professions (Singer, Magician, Acrobat) but no new skills. I'd rate, in order of decent for Dynasties, World Adventures -> Showtime -> Generations -> Late Night
Of course, this could all easily change with Supernatural and Seasons.