Tough, tough topic.
In no particular order.
Justified - this is probably more of a guilty pleasure than favourite, but it does have the current best theme tuneof any tv show.
Battlestar Galactica (reboot) - After my initial displeasure of making Starbuck and Boomer women, I got over it and gave it a chance and haven't regretted it since.
True Blood - Brought Vampires back from being sparkling little bitches. Also points for a great theme tune
Twin Peaks - A great mystery that was just out at the right time for me to really be taking an interest in film/television beyond special effects and stunts
Babylon 5 - This had what Star Trek was missing, a grimness. Although DS9 was the better for having this for comparrison/competition.
Honourable mentions
Firefly (the only reason this isn't in the main list is because of the low episode number)
Dexter (only one below par season nemesis)
Oz (if this doesn't give you pause for thought before breaking the law, nothing will)
Buffy tVS/Angel (this was in the main list, but for how much I've enjoyed it and some great episodes and writing it just doesn't quite belong at the top)
Strike Back (boys own adventure type malarkay that only has a very tenuous awareness of reality, it's great fun though)
Space: Above & Beyond (interesting riff on WW2 stories, but again too few episodes [Fox strike again])
Castle (good fun, but not quite good enough to go into the main list)
Sons of Anarchy (no particular reason, but the subtlties of the writing and acting are very good)
Grimm (only part way through the second season, but with more of the same calibre then this could replace something in the main list)
Walkin Dead (just because)
Magnum P.I. (just about the only show from my childhood that isn't too hokey or cheesey)
Boardwalk Empire (interesting, that this period of history isn't familiar for me. Richard is now one of my favourite all time characters)
Legend of the Nine Tailed Fox (A Korean fantasy story that would probably appeal to those that like Buffy/Grimm)