There are three separate Evangelion movies. "Evangelion: Death and Rebirth", "The End of Evangelion", "Revival of Evangelion". Each are desribed in turn, along with any variations of them that exist. Only the Japanese Releases are detailed here.
Evangelion: Death & Rebirth
Premiered March 19, 1997
A few weeks after the conclusion of the Evangelion TV series air in Japan, it was decided that two movies would be made for spring and summer of 1997. Gainax said that the first one would be a sum-up of the series, while the second would be an "Original Story".
Eventually it was decided that the first movie, called "Evangelion: Death and Rebirth", would consist of two parts, Evangelion: Death and Evangelion: Rebirth. Of these two parts Evangelion: Death was designed to be a re-cap of the series while Evangelion: Rebrith was planned to be the new Evangelion Episodes 25 and 26. However because of schedule problems (yet again), Gainax announced that "Evangelion: Rebirth" would only be the beginning of the new ending.
"Evangelion: Death" was directed by Masayuki, and is a digest of the first 24 episodes of the TV series. It is 60 minutes long, approximately 40 minutes consisting of "old" footage from the TV series and the other 20 comprised of new footage. Most of this new footage had been produced for the Japanese Video release of Genesis 0:11 and Genesis 0:12 (which contain episode 21 to 24). At the time of Evangelion: Death's release Genesis 0:11 and Genesis 0:12 had not been released.
Evangelion: Death (True)
Screened on the 2 January, 1998 on the Japanese Satellite TV Vhannel WoWoW this version of Evangelion: Death was re-edited personally by Masayuki. It appears that Masayuki really didn't want to include all the excepts of the new scenes from episode 21 to 24 becuase he removed some of them from this new version of Evangelion: Death.
Both Evangelion: Death (True) and Evangelion: Rebirth were screened at this time, but no changes were made to Evangelion: Rebirth.
Evangelion Death (True)^2
In March 1998 they released Revival of Evangelion which contained yet another verison of Death, titled "Evangelion : Death (True)²". This was an improved version of "Evangelion : Death" which was edited personally by Masayuki again in which only minor changes were made to the music and sound.
First premiered March 19, 1997 with the release of Evangelion: Death & Rebirth and also screened again on the 2 January, 1998 along with Evangelion: Death (True), Evangelion: Rebirth contained completely new footage. It was originally supposed to contain the entireity of the new episodes 25 and 26 and be a complete conclusion, however becuase of production issues it was decided to make it only the first two thirds of the first part of the final conclusion, with the actual ending, The End of Evangelion, being released later that year.
The End of Evangelion
The End of Evangelion first premiered in Japanese theatres on July 19, 1997, 4 months after the realease of Evangelion: Death & Rebrith. This second movie was designed to be the complete new ending. It was originally titled "Evangelion: Rebirth II" however they finally decided on the (in my opinion much better) name of "The End of Evangelion".
The End of Evangelion consists of two parts, Episode 25': Air and Episode 26': Magokoro o, Kimi ni. These two "episodes" are designed as replacements or alternatives for the original episodes 25 and 26 and the apostrophes are used to denote that they are the movie versions of those episodes. These episodes continue stright on from where the last scene of episode 24 left off. The End of Evangelion was created as a remake of the last two TV episodes and so the TV episode format is used within them, with each episode having its out subtitle and eyecatch scene.
Episode 25': Air
The title of this episode is "Dai 25 Wa: Air" (25th Episode: Air) and has the eyecatch "Episode 25' Love is destructive." The first two thirds of this episode had already been shown in part in Evangelion: Rebirth. However about one quarter of this repeated part from Evangelion: Rebirth was filmed again or remade to improve the quality. A few scenes were added in to this repeated part that were not in Rebirth at all and also new musical tracks were slected for this repeated part with Rebirth. So even though Episode 25': Air does repeat for the first two thirds footage shown in Evangelion: Rebirth, there are a number of changes.
The script for Episode 25' "Air" is based on the original script for episode 25 which had been completed during the TV series production. Beuase of production issues this script wasn't used in the TV episode 25 but was kept and used as a base for the movie Episode 25'.
Episode 26': Magokoro o, Kimi ni
The title for this episode is "Dai 26 Wa: Magokoro o, Kimi ni" (26th Episode: Sincerely Yours - My Pure Heart For You) and has the eyecatch "One More Final I need you.".
In contrast to Episode 25': Air, the script for this episode was based on the "inner world" one of the original Episode 26, however it was expanded on to add much more "real world" story information and dramatic content. All off the footage for this episode is new, none of it at all being shown in Evangelion: Rebirth.
The End of Evangelion: Theatrical release Vs. Video release
The End of Evangelion was released in video in two parts in Japan.
"Genesis 0:13" featured episode 25 and episode 25' and "Genesis 0:14" featured episode 26 and episode 26'. For their Video release the episode contained within "The End of Evangelion" were altered slightly to be more in form with the video style of episode. Below is a list of the changes between the Video version of each episode and the Theatrical Version.
The Video Version of Episode 25':
Eye catch: "Neon Genesis Evangelion Episode: 25' Love is destructive."
Credits for just episode 25 are shown at the end to the song "Thanatos - If I Can't Be Yours - (Short Version)"
At the end of the episode there is a preview of the next episode.
The Video Version of Episode 26':
Title screen: "Neon Genesis Evangelion"
In the kitchen scene Asuka's "Iya" (No) is written on the screen, we don't hear it.
Eye catch: "Neon Genesis Evangelion One More Final: I need you."
The caption at the conclusion of the episode says simply "End"
Credits for just episode 26' are shown at the end to a string version of "Jesus bleibet meine Freude"
The Theatrical Version of Episode 25':
Eye catch: "The End of Evangelion Episode:25' Love is destructive."
Credits for both episodes 25' and 26' are shown at the end of episode 25 to the song "Thanatos - If I Can't Be Yours"
There is no preview of the next episode.
The Theatrical Version of Episode 26':
Title screen: "The End of Evangelion"
In the kitchen scene Asuka's "Iya" (liar) is said and not written on the screen.
Eye catch: "The End of Evangelion One More Final: I need you."
The caption at the conclusion of the episode says "End of the movie"
There are no ending credits, just a black screen.
Revival of Evangelion
March 7, 1998
Revival of Evangelion was the third Neon Genesis Evangelion movie to be released in Japan.
Revival is ultimately the "final vision" of GAINAX and Anno Hideaki. It combines parts of the first two movies, Evangelion: Death and Rebirth and The End of Evangelion, into one long production. Revival is how the Eva movies were supposed to be released if GAINAX didn't have all the money and scheduling problems it did. It is a "complete" ending, "This is the ending you were asking for".
Revival of Evangelion is was released in Japan on March 7, 1998 and it contains the following:
Evangelion: Death (True)²
Episode 25': Air
Episode 26': Magokoro o, Kimi ni
This is basically just Evangelion: Death (True)² plus The End of Evangelion. It contains no "original" Evangelion: Death, no Evangelion: Rebirth and no new scenes. It is just the combining of all the parts into what was originally envisioned.