First of all, the biggest difference between Naruto and Shippuuden is the darker tone, the maturity and the depth in Shippuuden. In Naruto, the whole series was about him wanting to become the Hokage, being clumsy and always working hard to become better than Sasuke.
I loved Naruto's dorkiness but in Shippuuden he becomes serious. The series as well. Now the friendship and loyalty takes over. The mysteries get their answers and new questions take form.
Akatsuki, the moon plan, Madara, war... the thrilling surprises, the horrifying reveals, the cliffhangers... these things are what makes Shippuuden one of the best animes I know. Kishimoto has built this massive foundation for us to walk on during the first half, and now he slowly digs into the core of the story. It keeps you on the tip of your toes. That's why the story itself gets a 10/10 from me. Story (10/10)
Of course the art is much better than Naruto. Shippuuden has much more attention for details, the characters' outfits are much better made, the colouring and effects are so much better animated. The landscapes are beautifully drawn. Fighting scenes and emotional scenes are something I've noticed myself are paid much more attention to. The characters movements flows better.The realistic feeling is all over Shippuuden. Great! Art (9/10)
To be honest, I prefer not to notice the sound at all. Sound in movies and series shouldn't be noticed. The music is there to strenghten the mood. And since I don't notice the sound and it makes me feel what I'm supposed to feel, I guess the sound is well picked. I really liked the piano pieces in Naruo. Grief and Sorrow is an extraordinary piece. But I especially enjoyed the Pain soundtrack with the choirs and dark pipe organs in Shippuuden. Sound (8/10)
In Naruto and Shippuuden, Kishimoto is very focused in telling all characters stories. All characters have their backgounds and special personality. They all feel like real people that you know and they all grow throughout the series. You follow their Changes and that's what is so great and important about a series that is this long. The character development. (10/10)
So, to justify and defend Shippuuden...
First of all, you have to understand the use of fillers. With an anime this long the writer can't keep up with the pace. For every episode they use about 2-3 chapters of the manga. When the anime has reached too far, they have to buy time for the writer to write more. Or, they could make it like many other animes... Make up another story and end for it or just pause it for a couple of years while Kishi draws the manga like crazy. But that wouldn't make anyone happy. Please, stop going on and on about the fillers. They are there for a very good reason.
Naruto goes from a clumsy kid who only wishes to become the Hokage, to a serious, hardworking, loyal friend who doesn't only want to save his friend, but also the whole ninja world from the neverending cycle of hate and despair. I enjoy the series extremely much and I hope that you do too. ^^
