I'll start by saying that, at first, I didn't like the show, it seemed like a bounch of episodes of poor sci fi fixed togheter in low budget episodes. In fact, I still think that, in order to understand and appreciate this series WITHOUT the films and rebuilds, you need to think of it as the first perspective as it follows:
First perspective: the whole series is "humans trying to find their true self". Therefore, this finale is truly fullfilling and makes sense as a whole. Sure, some things do not catch up, and a lot remained unanswered: what are the Angels, why are they here? Where do they come from, how did Adam appear into this world? But, at the same time, this Shinji problem with his personality is something we all have... and you can find pieces of the finale trough the whole series, therefore, the finale is a masterpiece;
second perspective: if you take the series as sci fi series, it's pretty messy and... bad, honestly. Until episode 11, everything seems just a bounch of episodes linked togheter by the same world and characters, but the Angels do not have a meaning, and appear for no reason at all, for no purpose at all if not reach Adam. Why? So much remained unanswered. Then, the plot gets better, but the problem is that, with such developement, you would need a different tipe of finale.
Therefore, since I am all for this kind of endings, I like to think at the series as the first perspective, therefore I loved this finale. But, again, so much remained unanswered. That's why, as far as I can consider this episode sooo good, I, at the same time, think that some more episodes where needed in order to explain things once and for all.