I don't usually get that invested, but I do enjoy watching certain TV couples - usually the more creative ones that aren't coated in overemotional drama.
Pushing Daisies - Ned and Chuck
The Big Bang Theory - Penny and Leonard
LOST - Jack and Kate, especially in season 1
And obviously Peter and Olivia - I thought they'd be interesting together from the first episode, even when I was convinced they were going to save John Scott.