The 1977 Star Wars IS a copy of a Japanese film from 1958 anyway.
Star Wars was inspired by
Hidden Fortress, but I wouldn't go as far to say that it copied it. George Lucas addresses the influence of the film in this video: youtu.be/TEJ6CzG9zVc
I watched
Hidden Fortress a couple of days ago for the first time and found these similarities:
1. HF: war time; ANH: galactic civil war
2. HF: 2 desheveled, comic men (Tahei and Matashichi) walk through desert having escaped battle; ANH: Droids C3PO and R2D2
3. HF: Tahei and Matashichi come across a dead body and consider searching the body for goods; ANH: R2D2 observes an unconscious Luke Skywalker
4. HF: Tahei and Matashichi separate; ANH: R2 and C3PO separate
5. Tahei and Matashichi are captured individually by the enemy; The droids are captured individually by jawas
6. Tahei and Matashichi are reunited; R2 and C3PO are reunited
7. There's a bounty for Princess Yuki, a young woman; The Empire seeks Princess Leia, a young woman (also, there's a bounty for Han by Jabba the Hutt).
8. The samurai wear armor; the stormtroopers wear armor
9. Tahei and Matashichi escape; the droids are freed from the jawas when Owen Lars purchases them
10. Both films use a lot of wipes
11. They meet a heroic man (Rokurota) possessing treasure; The droids meet Obi-Wan who has access to vital data
12. Tahei and Matashichi and Rokurota are trying to get home; Obi-Wan and the droids are trying to get to Alderaan.
13. Tahei and Matashichi discover that Rokurota is a legendary general; Obi-Wan is a legendary general from the Clone Wars
14. Tahei and Matashichi argue a lot; the droids argue a lot
15. Princess Yuki is not a damsel in distress; Leia is not a damsel in distress
16. The general is (at one point) interested in the reward; Han wants "reward".
17. The hidden fortress is destroyed; Alderaan is destroyed
18. They are spotted by scouts, the scouts flee and Rokurota chases them; The Millenium Falcon is spotted by Tie-fighter scouts; the tie-fighters flee, the Falcon chases them
19. Rokurota ends up (seemingly by accident) in the enemy camp; The Falcon accidentally ends up in the Death Star
20. Rokurota is challenged to one-to-one spear combat by the enemy general; Obi-Wan is challenged by Darth Vader
21. Tahei and Matashichi hide in a town; Droids, Luke and Ben hide in Mos Isley
22. Princess Yuki reclines in a certain way; Leia reclines in a certain way
23. Principle characters gather in one shot; same.
So there are a lot of similarities. However, there are more dissimilarities. In fact, if I had watched
Hidden Fortress without being told it influenced Star Wars, I probably would not have made the connection. First of all, they are completely different genres. Second, one is set in 19th century Japan, the other long, long ago in a galaxy far, far away. Third, the battles in Hidden Fortress are short, whereas the battles in SW are long. Fourth, there's nothing supernatural in HF; in SW there's the Force. Fifth, the characters are very different.
If we compare Episode 4 and 7, however, the similarities are striking. Normally this wouldn't bother me, but this is STAR WARS we're talking about here! Abrams had 30 years to come up with something new and fresh to add to the saga, and this is what we get?! A droid with a spherical body and X-wings with black paint jobs?! Abrams dropped the ball and has ruined the franchise, imo.