Hey there!
Yes, "OVA" is "Original Video Animation". In a lot of Cases, OVAs are shorter than TV Series (but don't have to be!). They are called that way, because in Japan, OVAs are released on video FIRST, without being shown on TV prior to that.
Whether you should watch an OVA (or OAV, as they're also called) or a TV-Series depends on the series. Sometimes, one is better, sometimes, the other, sometimes they are connected, and you should watch the first before you watch the other. They can be connected in various ways (from playing in the same "universe" to putting the characters in a different setting and/or time) or have not much to do with each other. (Afaik, Tenchi is a good example here). There are also Standalone-OVAs, aka OVAs without a TV-Series in the same universe.
To get more information on series (and what to watch), look on pages like
www.animenewsnetwork.com or
www.anipike.com .
And some personal ideas on what you might like from me (verrry subjective, but also based on your tastes, as far as I can guess them from your list).
You seem to like SciFi and Fantasy a lot, and you've also seen some of the classics.
Try:
- Slayers/Slayers NEXT/Slayers TRY (in that order, those are the 3 Slayers-TV-Series)
- Silent Möbius (The TV-Series, I heard the movies look better, but the storyline falls short)
- Princess Mononoke (THE Miyazaki-Movie in my opinion - beautiful art and a great storyline!)
- Those Who Hunt Elves (be sure to get the first one, as there are already two Series!)
- RahXephon
- Oh! My Goddess (Shoujo-ish, but funny and a classic! I'm talking about the 5-Part-OVA first, not the Mini-Goddess-Adventures.)
Like I said, very much tainted by my own opinion - but as our tastes don't seem to differ an awful lot, you might like those series!
Greetz,
Shilahr