Most american viewers love 1x03, 2x01, christmas episode, 3x01 and 3x04 and I'm not sure about season 4 yet. I tend to disagree a lot with american viewers.
My favorite ones are 1x01, 1x02, 3x03, 2x02 and 3x04 in that particular order. I do not consider the chritmas episode to be as great as everyone else calls it, because I think only half of it was actually very good and the first half was predictable and meh (also Chaplin was terrible in this episode). I also disagree with Nosedive a lot, I do like it but is one of the weakest episodes IMO.
Be right back was so good in the beginning but the last 20 minutes or so... idk, I didn't like the ending at all
