Doctor Who has joined a long list of shows that I have given up on at one point or another. If I am bored out of my whits for three weeks or more, I usually decide to just stop watching. So, now you'll be spared with my analysis of the episodes. Of course, since nothing else is really going on in my life, that will take away half of my recent posts of the past half year or so. Oh well.
Battlestar Galactica - I stopped with 8 episodes left!
Ugly Betty - I would skip almost everything except the Marc, Wilhemina, and Amanda scenes and just decided to not bother anymore.
Star Trek Voyager - although, I think I've overheard every episode since
Robin Hood - once I got back to the US and had a life, I couldn't stand the show anymore. Although, I do like the music.
Will and Grace - do I really need to explain?
CSI - for a time, I was really in to murder mystery shows. no longer. I think my disdain began when they started delving into the private lives of the characters. I didn't care.
Cold Case - same reason as CSI
Modern Family - granted, this is very recent.
These are just a few I can think of off the the top of my head.