Neon Genesis Evangelion <TAG1> is a cult anime that has multiple versions and alternate endings. If you want to understand all the chaos, here are the main viewing options.
Classic Order (original + film)
Neon Genesis Evangelion (1995) – 26 episodes
The End of Evangelion (1997) – alternate finale instead of series 25-26
This is the canonical viewing path that best conveys the original story. The series gradually immerses you in the world, and The End of Evangelion expands the final.
For those who want to see more
Neon Genesis Evangelion (1995) – 26 episodes
Neon Genesis Evangelion: Death & Rebirth (1997) (retelling of the first 24 episodes + some extra content) - if you find a place to see
The End of Evangelion (1997)
There are many different things written about the title Neon Genesis Evangelion: Death & Rebirth. Someone says it was a marketing ploy to warm people up before The End of Evangelion (EoE) was shown and it is not mandatory to watch. Someone writes that the added scenes reveal the story a little more. So it's better to look and argue about whether it was worth watching. If you find a place to watch, because I could not find this title on streaming services.
Rebilds (alternative version of the story /tetralogy of films)
If you want modern animation and a slightly different development:
Evangelion: 1.0 You Are (Not) Alone (2007)
Evangelion: 2.0 You Can (Not) Advance (2009)
Evangelion: 3.0 You Can (Not) Redo (2012)
Evangelion: 3.0+1.0 Thrice Upon a Time (2021)
These rebilds (Rebuild) they start as a remake, but gradually move away from the original story and give a new ending. It is recommended to watch after viewing the original/canonical story.
The best option for the first viewing is Evangelion
Neon Genesis Evangelion (1995)
The End of Evangelion (1997)
Rebuild of Evangelion (2007-2021) – if you want to see a remake/rebuild and new animation