Prison Break - first two seasons
Lost - first 3 seasons.
These are by far my favorite. I love when a show gets me really hooked, I just can't stop watching. And no other show did it like those seasons of Lost and PB.
I also absolutely love How I Med Your Mother. For very different reasons, and these last 2 seasons are pretty weak. Yet I still love it.
Did you watch 24 and Dexter?? They're kinda fast paced and with a lot of twists too, they're similar in a way.
Lost and Prison Break first few seasons are very addictive, but after the seasons you mentioned they decline a bit.
Anyway, Prison Break's first season is a real masterpiece, ine my TOP 3 of any TV show.