Off the top of my head, in no particular order
1) Legend of the Galactic Heroes - Great space opera, probably the largest space battle scenes in sci-fi anime, great stuff in general.
2) Robotech - Another good space opera with huge battles. My preference for the 1st and 3rd season.
3) Macross, Macross 7, etc - Basically what Robotech ripped off their 1st season from. I didn't really like Macross 7, as they took the entire music bullshit too far. There's a few other anime OVAs based on the classic macross era.
4) Macross Zero, Macross Frontier - More recent macross anime. Zero had only a few OVAs, Frontier lasted only one season only. Watchable.
5) Gundam (the older ones) - Tried watching the first gundam and it was kind of cheesy. There's a few newer gundam anime that seems to be centered around some gladiator-style duel... which did not catch my interest.
6) Gundam SEED, Gundam SEED Destiny - More recent gundam anime. Despite taking place only in the solar system, it's a pretty good watch with some nice space battles.
7) Ghost in the Shell - Cyberpunk genre. The anime movies were good, the anime series were even better. No space opera but definitely futuristic.
Did I miss out anything?
