Widely considered to be one of the best anime of all time, Evangelion still holds up today. At a glance the show is about 3 teenagers fighting in giant mechas as the earths first, last, and only line of defence against the worst scum in the universe, but really the story and themes go much deeper. The story goes that the creator Hideaki Anno had a mental breakdown while making the show, and managed to capture the essence of his existential crisis and distil it into story magic, like lightning in a bottle. Keep in mind the epilogue takes place in a movie called The End of Evangelion. The series won't make much sense without the movie.
Groundbreaking anime with fanstastic visuals and a good story, gets pretty philosophic towards the end but is definitely worth watching (maybe even a few times)