I thought the same of alphas at first but gave it a chance and it shone.
True blood if you're into the sex and blood thing (although everything past season 3 is a bit of a joke). and don't watch if you're not a fan of 'deep south' accents.
Defiance is a bit pish, considering the backing it had.
Prison break went on 2 seasons too long.
Castle is a good choice, lots of Firefly references. (also, that Red-head daughter ages well throughout the series, and the cop is haaawt)
Battlestar Galactica (endure the middle seasons, the last couple are superb).
Caprica (another one that got canned that had potential, again endure the 'Angst' and you'll be rewarded).