Is very difficult to me to say what is my favourite serie because since I have netflix I watch a lot of series like Dr. House, Walking Dead and Breaking Bad (the last one I started to watch a few weeks a go and I can't stop to watch it).
But definitely, my favourite serie (at least for the moment) is How I meet yor mother. I loved all the characters since the first episode. This serie it have 9 seasons and I start to watch it in the summer. It took me like 3 months finish to watch it.
The serie is about a man that narrate to his children the story of how he meet they mother, but he tells a lot of details so the story stretch on 9 seasons. The name of this man is Ted Mosby who is an architect and the story start when he lived in a loft in New York with his best friend Marshall and Marshall's girlfriend Lilly. They usually went to a bar and in that place they meet Robin who becomes in the platonic love of Ted, but they have a lot of obstacles that impide them to be together. Besides, in the bar they meet Barney a ladies'man who becomes in a friend of the gang.
I think that my favourite episode is the last one when Ted finally finished the story of how he meet the mother of his children whose identity is reveled in the last season and sadly is not Robin, but in the last episode he reveal that the mother of his children was dead and the purpose of tell this story to his children is that he want ask them if they were ok if he date to Robin, and they gave him their approve.
I liked watch this serie because is very realistic in matters of live like love and friendship and I definetly recommend you to watched it.