I've decided to extend this a little bit to include 10 other shows before going into the other 25 I have as my favourites.
Dollhouse - Victor/Sierra
The show might have lasted two seasons but Joss Whedon managed to give us at least one couple worthy of rooting for. Both Victor and Sierra had the best chemistry with each other and definitely were the couple to watch on this shortlived series.
Will And Grace - Will Trueman/Vince D'Angelo
After spending the first five seasons flitting between boyfriends, the writers finally gave Will someone who complimented him and while him and Vince had their ups and downs, it's a credit to the series for this great relationship.
The L Word - Bette Porter/Tina Kennard
Relationships in this series were ten a penny but Bette and Tina were definitely the long haul relationship of the series, both with it's good and with it's bad moments. Still, they were definitely the best of a mixed bunch of couples on this series.
Alias - Sydney Bristow/Michael Vaughn
Bucking something of a trend here, Sydney and Vaughn for me were actually a pretty good couple. Sure we could've done without Lauren during S3 or Vaughn's fakeout death for most of S5 but other than that, I liked these two.
Shameless - Kev Ball/Veronica Fisher
The not so married but chaotic couple were a joy during the first three years of the series and while both Dean Lennox Kelly and Maxine Peake seem to be constantly getting decent roles after leaving the series, I do sometimes miss the pair.