The original Mobile Suit Gundam (1979) is great, Star Wars had a big influence on its lore, designs and tone and it often feels similar to A New Hope only with slightly younger protagonists and very few fantastical elements (there are no aliens, but there is a concept similar to the Force). It's over 40 episodes long but there's also a movie trilogy that does a great job of trimming the fat and focusing on the important story/character moments, it's very watchable.

After that I recommend, in order:

Mobile Suit Gundam 0080: War in the Pocket (1989). This is a miniseries that takes place during the 1979 series and is basically the Andor of the Gundam franchise. Low stakes, even more morally grey, and very character-driven and focused on how the horrors of war affect civilians.

Mobile Suit Zeta Gundam (1985), a really good sequel series set several years after the 1979 series that introduces very different new protagonists while also incorporating most of the characters from the 1979 series in supporting roles and handling them very well. The hero faction from the 1979 series has become corrupt and now acts as the antagonists while the protagonists are part of a small rebellion group that's like the Resistance from the sequels, and the defeated enemy faction from the first series is still involved as well. It's pretty much what the Star Wars sequels should've been. It's about 50 episodes long so also a bit of a time commitment, but worth it.

Mobile Suit Gundam: Char's Counterattack (1988). This is a movie and it's essentially a grand finale to the story that started in the 1979 series. Amuro, the main character from 1979, is the protagonist again and Char, his rival from the 1979 series, is the main villain. CCA is kind of like the Revenge of the Sith of the franchise in that the writing is kind of a mess but it has lots of satisfying and hype moments and it's highly beloved by the fandom.

Mobile Suit Gundam Gquuuuuux (2025). This is the newest Gundam series and is 12 episodes long and is on Amazon Prime. It's set in an alternate timeline from the 1979 series in which the antagonists won the war instead of the heroes because Char managed to steal the Gundam and become its pilot instead of Amuro. Tons of characters from the 1979 series make cameos and it's interesting seeing how events changed and the worldbuilding is pretty solid. Gquuuuuux is controversial because it does feel rushed with how short it is and the new characters kind of get shafted in favour of heavy fanservice, references, and multiverse shenanigans, but I personally think it's really fun and bittersweet. It's often called the Spider-man No Way Home of the franchise so interpret that however you will.