As for the Dexter series, I would recommend getting back into it. You will regret not watch season 4, even if season 2 and 3 arent that great.
The other shows..Im usually not one that gets into series like Lost, or any of that stuff. It took me forever to get into Dexter..in fact I think the 4th season was already over, but since it had to do with a serial killer (which is something I find very entertaining to read/watch) I decided I finally had to see what it was about. No lie I finished the 4 seasons in about 2 or 3 weeks