Really? Prison Break ran out of steam after season 1! And by the end of season 2, I was done with it. You must have a really low standard!
Most TV shows run out of ideas after a few seasons, The Walking Dead being a prime example. I used to be CRAZY about it. The first season was great, second was total meh, third, fourth and fifth were relatively decent. But by the time it reached season 6, I completely lost interest because of sheer repetitiveness.
And Prison Break, for me, was no exception. Same old story again and again and... AGAIN!
I love zombies in fiction, might even love them in real life () but... That show made me HATE them. Why do they always show-up in the wrong place at the wrong time and eat the people you care about the most?!
About the only show (Or sitcom) that kept going strong after multiple seasons is the legendary Two and a Half Men. It charged like a freight train till season 9, when Ashton Kutcher came along and ruined everything. Charlie Sheen is an A-Hole in real life, but I loved his character in 2.5.