5. Skins

The British teenage series Skins is the series for you to watch if you want some adolescent drama. But most of all, it is wonderfully British. We follow the adventures of a group of friends for two seasons, and then a new group of friends takes over. This happens after every two seasons. This series launched Kaya Scodelario's career, who is well-known for Spinning Out, Pirates of the Caribbean and The Maze Runner. The original release started in 20007 and finished in 2013.
4. Avatar: The Last Airbender

The best animated series ever, in my opinion at least. Many of my generation are able to talk along with the intro and have seen each episode at least four times. Avatar can be seen on Netflix in most countries. The original release started in 2005 and finished in 2008.
3. Nikita

One of my favourite crime series. Or at least one that had a very memorable story. Maggie Q dazzles in this exciting series that is filled with danger, murder, drama and tension. Definitely worth a rewatch. The original release started in 2010 and finished in 2013.
2. Revenge

This exciting series starring Emily VanCamp released between 2011 and 2015. The series revolves around Emily Thorn, actually Amanda Clarke, who is hungry for revenge after her father was wrongly imprisoned. All of this happens with the Hamptons as set pieces.
1. Grey's Anatomy
If you're talking about hospital series, Grey's Anatomy cannot go unmentioned. The series has already been going on for sixteen seasons. Who would've thought back in 2005 that Grey's Anatomy would be such a big hit? You should be able to last for a while, considering it currently has 360 episodes.
It could very well be that you've never seen these series, an even better reason to start watching. Many before you have already enjoyed these series. Do you have another series that you consider to be worthy of rewatching? Here I have some honourable mentions; fairy tale series Once Upon a Time, the horror series Penny Dreadful, the adventurous Terra Nova and the comical Don't Trust the B---- in Apartment 23. Soon there will be more top-fives for you to fill your time.