I have not that knowledge like some other have here in this thread but I guess I can explain you my opinion about this discussion.
NXT was the first POS.
Monero is something you can mine.
NEM will be the first Proof of Interest. I can see the quick proceedings in NEM. NEM brought already the alpha version. There is a great community standing behind this coin. Maybe bigger than in all other coin imo. But it is just what I guess.

Sadly I missed almost everything about Bytecoin. When came this coin up?

Dont forget I'm not that kind of pro like some others here and I'm not so often in btt but I'm very excited about some new developments.
I will keep an eye on NEM and NXT as the most popular second gen coins.