- Yamato (the 1974 version, 26 episodes for full authenticity or the 2012 remake). Has a real classic saturday-morning / space opera vibe. It's one of the most important series in the history of sci-fi anime.
Uchuu Kaizoku Captain Herlock - "Space Pirate Captain Harlock" in English, it's one from a manga by Leiji Matsumoto, the original guy behind Yamato.
- SDF Macross (1982: 39 episodes) aka
Robotech (Robotech was shoddily butchered when they "adapted" it however).
Macross Zero and
Macross Plus are standalone ~ 5 episode series that are tangential to the main plot in Macross and good starting points.
- Genesis Climber Mospeada (1983): adapted into part 3 of Robotech, it's the one with motorcycles which transform into jetpack power-armor. It's worth it just for that. It's pretty fun and straight forward "band of misfits vs the alien mecha" type stuff. It's a fun standalone one that runs 25 episodes.
- Gundam: it's a good staple. I've main stuck to the "Univeral Century" Gundam timeline, the other timelines are standalone spin-offs.
- Gundam 0079 (1979): the original core series of UC Gundam. If you want the main saga of a couple hundred episodes, you start here.
- Gundam 0080 : a short story that happens concurrently with the original series
- Gundam IGLOO: a 2000's CGI series of short films about various characters during the Gundam 0079 war. "Lone warriors dying in glorious battle against humungous mecha" is the theme here. The main thing I like about IGLOO is that it looks at the lives of the soldiers in the humungous mecha war that
don't have the security of riding a humungous mecha. This video is a good expression of the vibe in IGLOO:
https://www.youtube.com/watch?v=Gb9L94WRP20- Ginga Eiyuu Densetsu: a
glorious space epic. But rather than action, the focus is on politics and military tactics. It's galaxy-scale WWI in space with the UFP (allies) vs the Imperium (Prussian/imperial germany basically), with corrupt bureacracies and incompetent military leaders, with millions killed in pointless battles for
centuries. In this vista, two young officers rise through the ranks on both sides to face off as rivals in war. The series covers both their careers, so there's no real good guys and bad guys.