Lost- Season 1: 6 Episodes in, still incredibly good. They found the cave, fresh water, Adam and Eve. The first show I can remember where flashbacks did not bug me.
If I do anymore "Lost" talk I'll try to put it in the Season 6 Lost Spoiler thread last replied to by me in 2011 saying I was starting to watch reruns on Netflix. Well, I got distracted but am back at it again.
I watched the first 2 seasons of Lost, which I liked. After that it got pretty ridiculous in my opinion.