I wanted to watch Saint Seiya, but I found on Wikipedia that there are many series that make up the Saint Seiya franchise. So what's the order of it?
The main series is Saint Seiya which is an adaptation of first part of the homonymous manga by Masami Kurumada.
The second part of that manga was later adapted in three different series of OVAs which tells about the Holy War fought at the end of the 20th century between Athena and Hades:
- Hades: Chapter Sanctuary
- Hades: Chapter Inferno
- Hades: Chapter Elysium
This is the core of the story and is set in the 1990s. In the same period of time are set the four OAVs: Jashin Eris, Kamigami no Atsuki Tatakai, Shinku no Shounen Densetsu and Saishuu Seisen no Senshi-tachi.
Then there are the prequels:
- Episode G is set a brief time before the main story and tells stories about the youth of the Gold Saints.
- Next dimension is both a prequel and a sequel (it involves time travel): it is written by the same author of the original story and it tells about the Holy War fought 243 years before the main story.
- Lost Canvas is an alternative prequel (who was adapted by into a two series of OVAs) written by another author, which tells an alternative version of the Holy War fought 243 years before the main story.
The sequels are:
- Next dimension (see above)
- Soul of Gold is set in parallel to the ending of the main story and tells about the Gold Saints who are resurrected after their sacrifice at the end of the main story.
- Tenkai-hen an OVA set after the ending of the main story and sees as the main antagonist the God Artemis.
- Omega is set 25 years after the main story and tells about the "new generation" of Saints who will have to fight agains Mars and his warriors.
There is also a spin-off, called Saintia Sho set more or less in the middle of the main story, where the main antagonist is the Goddes Eris.
The following is a scheme showing how the various series are related.