The long running programme won the award ahead of Eastenders and Hollyoaks.
Chairman of the judging panal David Liddiment said the soap was "well-paced and dignified with artful touches."
He added: "This show knows its place in a vast market. With strong performances and a quality of writing, the stories enjoy constant injections of humour and retain a warmth which is enjoyed by all."
The awards ceremoney was held in London on Tuesday evening and was hosted by comedian Jo Brand.
Other winners included Games of Thrones star Sean Bean.
With strong performances and a quality of writing, the stories enjoy constant injections of humour and retain a warmth which is enjoyed by all.
David Liddiment, Royal Television Society
He was named best actor for his portrayal of a cross-dressing teacher in the courtroom drama The Accused.
The actor, who has played numerous gritty roles and made his name in the Napoleonic drama Sharpe, wore a mini-skirt, make-up and a blonde wig for the gripping performance.
Olivia Colman was named best actress at the respected awards bash for her performance in the same BBC1 series.
Ant and Dec took the best entertainment performance prize for a third consecutive year for their role as hosts of ITV's I'm A Celebrity ... Get Me Out Of Here!, while ITV2's Celebrity Juice was named best entertainment show.
Film-maker Danny Boyle picked up one of the two honorary judges' awards for his work on creating the Olympics opening ceremony.
The Royal Television Society paid tribute to the man who "masterminded the most surprising, dazzling, original night of television of the year."
- Actress: Olivia Colman - Accused II (BBC1)
- Actor: Sean Bean - Accused II (BBC1)
- Comedy performance: Jessica Hynes - Twenty Twelve (BBC2)
- Drama serial: Good Cop (BBC1)
- Drama series: Sherlock (BBC1)
- Entertainment: Celebrity Juice (ITV2)
- Entertainment performance: Ant McPartlin and Dec Donnelly - I'm A Celebrity ... Get Me Out Of Here! (ITV)
- International: Girls (Sky Atlantic)
- Live event: London Olympics 2012 (BBC)
- Popular factual and features: Long Lost Family (ITV)
- Presenter: Clare Balding - The Olympics (BBC)
- Scripted comedy: Alan Partridge: Welcome To The Places Of My Life (Sky Atlantic)
- Soap and continuing drama: Coronation Street (ITV)
- Writer - Comedy: The Thick Of It (BBC2)
- Writer - Drama: Steven Moffat - Sherlock (BBC1)
- Judges' award - Channel 4's coverage of the London Paralympics 2012
- Judges' award - Danny Boyle
- Lifetime achievement award - Dave Gordon (BBC sport)