The first two episodes kind of felt like a (well executed) sitcom at times. But it was nice, the characters are great and their chemistry is well done. But episode 3 onwards is where the excitement kicked in for me. How all the plotlines escalate into the final act is really well done and suspenseful. Some parts reminded me of Jurassic Park, actually. The ending had a surprising emotional weight to it, it definitely got to me. I think season 3 is quite a bit better than season 2, but season 1 remains my favourite.
The first season offcourse has the advantage because as a viewer you are totally in the unknown and the mystery is more intriguing. But as sequels, they did both seasons 2 and 3 right. The focus on the characters is paying off. Instead of thinking up some new story where the old cast magically is involved in (what happens a lot in sequels), all situations are further escalations as a result of the events before. And how the characters are growing up feels on point as well, these children are really doing a great job and their chemistry is fantastic. Especially the actress of El pulls of some amazing scenes.