The Aria series goes completely unoticed by many, which saddens me as I believe it to be one of the greatest anime ever created.
Story
The majority of the Aria series is divided up episodically over three seasons (I know people who have tried watching Origination first w/o viewing the first two.). Each story unfolds a whole new adventure for the characters to explore. The first two seasons, Animation and Natural respectively, are about introducing the characters and learning about the world which surrounds them. A series completely made of up small special adventures. As for Origination, being the third and final season, the second half becomes more linear and appears to have an objective in mind. The end of each episode always packs some sort of "special moment" or "wonderful message" which include things from abstract ideals to truths which may feel are obvious or hear all the time, but simply forget. Some may be turned off by its episodic nature, but I feel that it adds to the experience yielding great satisfaction by the end.
Aesthetics
In Origination, we recieve a nice upgrade in visuals. It flows much smoother than the first two seasons and appears much clearer. The character designs, as bland as they may seem, seriously fit the show's lighthearted and simple nature. The town of Neo-Venezia is also designed beautifully featuring pretty realistic European architecture. Overall, the animation is splendid as some refer to it as, "scenery porn." As for a series revolving around rowing gondolas, the water is also done especially well without looking too choppy.
Sound
The sound is probably one of the strongest aspects of the entire series. Throughout all three seasons, I have found nearly every single Aria soundtrack to be absolutely pleasant to listen to. It works perfectly together with the visuals to create a somewhat mystical, nostalgic and peaceful atmosphere. The OP and ED are once again great and music is used just at the right times to really add to the experience. It perfectly executes the tone of the show as lighthearted and optimistic.
Characters
The characters seem generic at first, but they are really what drive the show forward. Aria follows three girls, Akari, Aika and Alice, all friends working at different Gondola companies. Akari is an optimist who always stays happy no matter what happens. In fact, she may possibly be the most optimistic character I've seen in anime. For most of the series, he character is consistent, but recieves great character development by the end of Origination. Aika, on the other hand, has a more realistic outlook and often tells Akari to shape up. Her character is wary of what others think of her and she often attempts to be more, "mature." She also receives a great heap of development throughout the series. The final main character is Alice who is the underclassman of Akari and Aika. However, by no means is she looked down upon. She is intelligent and is probably the most skilled of the three at rowing. Everyday, she has her own personal goals to accomplish. As with Akari and Aika, she also matures throughout the series. The cast size is overall not super large, but has enough characters who reappear from time to time. I honestly can't say there a character who I hate in the Aria series.
Overall
At the end of the day, the Aria series is one of the greatest shows I've come to experience. I can easily place it within my Top 5 Anime. It performs outstandingly in all categories. However, it's appeal is definitely not universal. If you enjoy series with more action, suspense and big chests, then that's unfortunate because Aria has none of it. I can say that it's extremely slow-paced, has no action, violence, nudity or any questionable content of the sort. Aria requires an specific taste to enjoy to the fullest. As for me, there aren't that many series that I can easily say are as powerful and satisfying as Aria. It does deserve more recognition, but I doubt it has the chance of going mainstream considering its limited appeal. Feel free to disagree with me, but it will take a whole lot to knock this show off my favorites.
If you do enjoy Slice of Life series, then you're in luck because I hail Aria as the absolute pinnacle of the genre. It accomplishes so much and is an unforgettable experience.
If you do consider watching Aria, I definitely recommend viewing the first two seasons, "Aria the Animation" and, "Aria the Natural" before watching Origination due to requiring a large amount of buildup before delivering its phenomenal finale.