Arc 1: Intro arc to this Naruto shit. We get his first "nakamas" Sasuke and Sakura. Oh and theres the bad ass mentor Kakashi.
Arc 2: They fight the first main villain Zabuza and his minions, Haku, Gozu, and Meizu. Gato and his two swordsman are sub villains.
Arc 3: A tournament arc, also the first arc where Orochimaru is the main villain. The henchmen they'll be fighting here are Dosu, Zaku, and Kin. We are introduced to more "nakamas" such as Kiba, Shino, Hinata, Neji, Rock Lee, Tenten, Shikamaru, Choiji, and Ino. Aswell as Gaara, Kankuro, and Temari.
Arc 4: Turns out Gaara is the boss (Like how Tenshinhan was the boss of the Tenkaichi Budokai 22 arc from Dragon Ball). Plus Orochimaru is the main villain and is doing that invasion shit screwing the tournament up. Naruto and Gaara still fight. Spoiler alert, Orochimaru kills the third hokage.
Arc 5: Two of the Akatsuki's, Itachi and Kisame show up. But they're not the main villains. Orochimaru still is, but he's taking a break.
Arc 6: Orochimaru is still the main villain. Tsunade becomes the fifth hokage. The henchmen of who's in this arc is Kabuto who was introduced way back in Arc 3. Orochimaru gets his ass handed to him by Tsunade, but he is still the main villain after that. Kabuto gets his ass handed to him by Naruto, but will still play an important role in the story.
Arc 7: The first filler arc. Can't remember what it's about. The main villain in this arc is a filler villain, so he doesn't count.
Arc 8: Orochimaru is still the main villain, and the henchmen he unleashes on our heroes are Jirobo, Kidomaru, Tayuya, Sakon/Ukon, and Kimimaro. Sasuke makes Naruto butthurt by leaving the team. Kiba, Neji, Rock Lee, Shikamaru, Choiji and aswell as their allies Gaara, Kankuro, and Temari are the only ones fighting. Sasuke owns Naruto. Orochimaru is still the main villain and Kabuto is alive and well while being Orochimaru's bitch boy.
Arc 9-Insert that overused unfunny DBZ dubbed line quote about Vegeta getting pissed out squishing his scouter: You get this filler shit off of my internet. Oh and the villains in each of those arcs are whoever the fuck they're dealing with. They're filler villain, so fuck them.
Naruto Shippuden
Arc 1: Fuck me I quit.
Oh, and didn't Orochimaru and Naruto have some showdown where it's a tie, yet although Orochimaru still lives he isn't the main villain, just still lives and gets killed off anyways by Sasuke?