I've only played Birth By Sleep so I'm completely lost on the whole storyline but the gameplay is very fun and I had a blast playing it! I especially loved the two secret boss fights.
I loved what I played of the first one (I got to Neverland and then Summer was over...). Some of the boss fights could be infuriating though...
I liked the original back when I played it on my ps 2 a fair few years ago. Never really got into the sequels