If I'd rated this before season 3, this show would be an easy 10/10. But with each season after 2, the quality of the episodes continuously decreases with the occasional surprise, and then finally the mountainside plane wreck of season 5.

Season 1: 10 Season 2: 10 Season 3: 7 Season 4: 3 Season 5: 1

Averaged out (and weighted because seasons aren't all the same length) show comes to 6/10