Wow. It's really difficult to narrow it down to only 5. Here is my list-
Drama
1. Prison Break
2. Dexter
3. Newsroom
4. House MD
5. Breaking Bad
Other worth mentioning series are GOT, Sherlock and White Collar. Reason for not including Sherlock is, the episodes are just too less. And White Collar's starting seasons were average but the last two seasons were brilliant. About GOT, what I feel is while watching for the first time, it's really gripping. But, after watching once, I don't feel like watching again. This is how I rate. If I can watch the series again and again, it will be in my top list.
Comedy
1. Friends
2. Modern Family
3. Arrested Development
4. Coupling
5. The Big Bang Theory
Last season of How I Met Your Mother was sh##. It ruined the show for me. Same goes with Two and Half Men. After Charlie Sheen left, the show became less entertaining.