I have a rather huge collection of tv series. I'd suggest the following series:

Prison Break ( 3 good seasons, 4th one running now, not upto par with the other 3)

Entourage ( 4 awesome seasons, 5th one running now. Simply brilliant)

Battlestar Galactica (3 fantastic seasons, 4th one half done. Must watch for all sci-fi fans)

The Big Bang Theory (1 season, 2nd due soon)

Jekyll ( mini-series. based on the book, exciting adaptation)

The Andromeda Strain (mini-series. based on the book, again a very good adaptation)

The Lost Room (mini-series, amazing)

Breaking Bad (1 season, very good)

Weeds (3 seasons, 4th running, good stuff)

Heroes ( 2 stunning seasons, 3rd one due soon)

Dexter (2 seasons, 3rd running. Showtime is just too good)

24 (6 seasons, thriller plus action packed stuff)

Greek (1 season, 2nd running)

Til Death (2 seasons, sitcom)

Ultimate Force (3 seasons)

Hustle (4 seasons)

There's a whole lot of other series too, like Gossip Girl, Lost, The 4400, Roswell, Jeremiah, Kyle XY, Spaced, One Tree Hill, Scrubs, The Sopranos, Chuck, The IT Crowd, Black Books, Charmed.. I'd not be able to finish if i went on..

But if you need links or help with any related "issues", feel free to holler!