In 1988, a film was released in Japan. This film would later become a cult phenomenon in its coming years worldwide. This film was none other than Katsuhiro Otomo's Akira.
What can I say about this film? In anime fandom, this film is both influential and inspirational. There have been homages to this film, parodies, and much more. Akira is a post-apocalyptic cyberpunk action anime film based on Otomo's manga of the same name (which wasn't even finished by the time of the film's release). It centers around two teenage boys, Kaneda and Tetsuo. When Tetsuo begin to experience psychokinetic powers and is captured and tested by the government, Kaneda does whatever he can to rescue his childhood friend. However, things begin to change for the worst when Tetsuo begins to harness his powers.
Personally, despite the huge changes that Otomo made in the film adaptation of his work (which probably wasn't easy since the story in the original manga is pretty massive as I own and have read all of it), Otomo puts in the main aspects of the story into an understandable film plot.
The film had moderate success when it was released in Japan, but it wasn't that successful in theaters when it hit the American film market. The film became more successful within the home video market when it was released on VHS in the early 90s. It even got a LaserDisc release by the Criterion Collection, making it the first animated film to be given a released by the company until their Blu-ray and DVD release of Fantastic Mr. Fox.
The film itself is said to be the hardest to dub as the filmmakers decided to record the dialogue for the characters before animation began, and not the other way around like voice work for anime has always been done (where the animation is completed before the voices are recorded). The film has received two different English dubs: the 1989 Streamline dub, and the 2001 Pioneer dub (which I personally consider more superior than the one done by Streamline).
The film has even gotten the attention of Hollywood as Warner Bros. have tried for years to make a live-action adaptation. They eventually decided to have Taika Waititi direct the film, but said production had to be put on hold as he is currently making Thor: Love and Thunder with Marvel.
Otomo himself has even decided to go back, and make a new anime adaptation for television to make a more faithful adaptation of his manga as both his manga and film adaptation has gained more of a following over the years, especially as recent as this year as a 4K remastered version of the film was released earlier this year in Japan (and will be released on 4K Blu-ray here in the States this month).
No matter what big new anime film has gotten the attention of current anime fans, when I think of an influential anime title, I look and point to this one.