When I started watching it, Supernatural already had five seasons, at the beginning I didn't like it very much, but a lot of people were saying it's awesome so I continued to watch. The start (first couple of seasons) are kind of slow, though the story is still there and really very good, it is mostly episode-to-episode action which kind of irritated me. But once it picks up, you can't stop, you want to watch more and more. The monsters are always made great, with lore and stuff, the special effects are outstanding, the way the characters are evolving, oh my... You really get into the show, you almost feel as if you are a "hunter".
In the beginning everything is pretty simple - two brothers - Dean, the bad guy, and Sam - the guy who left the family "bussiness" for school, they don't like each other a lot, have a lot of grunts. But they unite in order to find their missing father. With the progression of the series they become best friends, Sam flings to the dark side from time to time and... I won't say no more, I hate spoilers...
Demons, angles, wendigos, strigas, djins, shapeshifters, arachne, banshee, hellhounds, demi-gods - this is just a small, and I mean a small part of what you will encounter and see in this series. If you like this supernatural stuff - watch it! If don't know if you like supernatural creaturs - watch it! There will be blood, gore and death! Peace guys, I'm out!
Sam Winchester: Why'd you let me fall asleep?
Dean Winchester: Because I am an awesome brother. What did you dream about?
Sam Winchester: Lollipops and candycanes.