Woo hoo! finally, FINALLY, my obsessive support of JRPGs by buying every obscure title no-one has ever heard of comes in handy! Bear in mind that this is only my opinion, but I've played the majority of the games you've inquired about, and will happily share my impressions:
time and eternity- The gameplay is decent, and actually tries to be interesting... sadly, the main character is unlikable, and the story is bland and forgettable. I DID enjoy how they played with the distressed dude trope at the start though. If you can get it for the cheap it may be worth a check, but I wouldn't pay more than 20 for it, if I had it to buy over again.
the hyperdimension neptunia games- there's a reason they developed such a strong cult following that they spawned an anime series. The combination of quirky characters with tongue-in-cheek story and a few loving jabs taken at gamer culture in general is undeniably appealing, and as far as budget JRPGS go, the gameplay is solid and enjoyable. be warned that the healing mechanic of the first game is legendarily frustrating, though this particular flaw is fixed in all later installments.
the arland saga (Atelier Rorona, Totori, and Meruru), and Atelier Ayesha I wish I could personally strangle the idiot executive who decided the one thing the venerable "Atelier Iris" and "Mana Khemia" games needed to become more awesome than they already were was to drown them in moe. That said, in terms of gameplay alone, these games come HIGHLY recommended by me. The atelier games are some of the greatest item crafting RPGs, and these installments are no exception. A strict timelimit can feel imposing at first, but as the series progresses it becomes less intense, though not as much fun as the game would be without it. Meruru also includes some city building elements that I found awesome. Just make sure you go into these games ready to roll your eyes at some annoying anime "cutesy" cliches.
the Agarest Wars games To know whether these are the games for you, I need to ask you a question attached to a scene.
Here's the scene: A still image of a cute girl trying to fit a sausage way too large for her mouth, into her mouth, while she and another, offscreen girl make innocent comments that could be construed as sexual innuendo.
Here's the question: Did the idea of that scene, and other scenes based around the same concept, titilate you enough to want to buy a game that revolves around them? If not, you'll probably want to pass on the agarest games. The stories are actually not horrible, and the game features a system where the story takes place over several generations of time, with each generation having multiple women you can marry, with your choice in partner deciding the stats, strengths, and appearance of the next generation's hero.
Sadly, as ambitious and interesting as this concept is, it's married to a bland, forgettable combat system, and a story that, while not horrible, exists primarily to convey ecchi scenes for those people who are into that sort of thing.
you've already recieved info on Valkyria chronicles and Disgaea, so just know that I, too, highly recommend them
Trinity Universe Been a long time since I played this one, but even acknowledging that, I'm amazed at how little I remember about it. I don't recall it being particularly unfun, but clearly it wasn't memorable to me... if you can get it cheap it would probably justify a playthrough.
Last rebellion No, this game is not good. I have nothing positive to say about it. From gameplay, to story, to characters. the best I can say about the high points of the game is that they're average. The worst things I can say of this game have no place in polite conversation.
The White Knight Chronicles I preordered the first game after seeing some awesome trailers and gameplay footage, and realizing how starved I was for a sweeping, cinematic JRPG experience that used to be so common back before the genre became niche. The game failed to deliver on my hopes. Visually it's excellent, but the gameplay is forgettable, and the story plays out like they had a checklist of every fantasy story cliche by their side as they wrote it. The crux of the game was designed to be played around online multiplayer elements that were poorly implemented, and the whole game just felt like it was overambitious, yet generic at the same time. My experience with the first game soured my desire to play the second, though I hear it was a vast improvement.
Tales of Graces Any "tales" game gets my approval. they're not all amazing, but even the worst of them are still pretty good. Graces is far from the best, I would actually recommend Xillia over it, if you can find it, but Graces is certainly worth a playthrough.
I hope I was able to help!