In opposite to their respective TV versions the two concluding movies of Evangelion and Ideon are similar in theme as well as imagery and even in music. The Ideon movie clearly inspired the epic conclusion of Evangelion.

A large part of Evangelion was inspired by Ideon to the point where it can be said that Ideon was the Evangelion of the 1980s that unfortunately never received the popularity or staying power of the latter.

Ideon and Evangelion share many similarities, the least of which is a similar troubled production schedule involving low raiting, decreasing budgets, an ending that due to said production troubles wasn't entirely according to plan, and a theatrical revival due to fan demand consisting of both a remastered recap movie and the originally intended apocalyptic finale. Ideon and Evangelion share many themes and concepts, and the ultimate finale for both look beautiful and still deeply resonate with the hearts of many to this day. If you liked one, you'll be sure to like the other as ell. Just make sure to watch the respective series for maximum effectiveness and impact, or failing that at least the corresponding theatrical compilation movies.

Hideaki Anno admitted to being inspired by Yoshiyuki Tomino's film. The crude and depressive atmospheres, the apocalyptic finale and visual metaphors pay homage to one of the best products of the 80s.

Space Runaway Ideon is one of the anime that inspired Hideaki Anno's Evangelion, and they both deal with similar themes. Both are dark and gritty science fiction anime, featuring destructive mecha and apocalyptic elements.

Neon Genesis Evangelion director Hideaki Anno has often cited Yoshiyuki Tomino's Space Runaway Ideon as one of his biggest and most important influences. Anno's directorial style is very similar to Tomino's style, with an overall very cinematic feel in their works, similar camera angles, and a very similar, clear, and often realistic scene presentations. Just like its predecessor (The Ideon: Be Invoked), The End of Evangelion is a dark and bloody film filled with plenty of deaths, and strong feelings of hatred and desperation, and in the end, everybody dies (or turns into orange juice, in Eva's case) in both films. Their endings, however, have some light and hope shining through. If you wanna watch something filled with deep, philosophical meaning and plenty of bizarre, mindscrew-ish imagery, then go ahead and watch either one of these movies, both of which I regard as masterpieces. Please don't forget to watch Neon Genesis Evangelion before The End of Evangelion and Space Runaway Ideon before The Ideon: Be Invoked. They both have their own respective compilation films, but neither one of them is a good replacement for the original TV series.