TNG: Shades of Grey
DS9: Melora, Rivals, One Little Ship, Hard Time, Far Beyond the Stars
VOY: [Any episode that did not hinge on Seven or The Doctor being the central character of either A or B story]
ENT: Terra Nova, Carpenter Street, Daedalus
I'd also like to add that I'm in complete agreement with BillJ
's original post... I've always found Star Trek rewatchable because it provides a great sci-fi escape and I'm sure it was designed to be rewatched so that little details could be appreciated; Star Trek is certainly not the first to use this kind of reward system in entertainment, but it is certainly in part the reason why we all post here.