Part 1: However this is a 'conversational' statement I would say my favorite villain in part one is a two-way tie. One is the obvious answer which is Orochimaru due to his cynical personality as well of have a highly capitalized relation with snakes which I naturally find sinister. He was also a powerhouse, able to fight Naruto with no hands while Naruto was in Kyuubi Mode.
My second choice is Itachi Uchiha; keep in mind this was before the revelation that Itachi was in fact loyal to Konoha and the true circumstances that caused the Uchiha Clan Massacre. I found his calm attitude while exemplifying all that is wrong with Sasuke Uchiha's life very attractive. Itachi was also exteremely powerful, literally bringing Kakashi and to a lesser extent Kurunei and Asume to there knees just by looking at them.
For part two, the position in my opinion goes to Nagato or Nagato under the guise of Pein. The Six Paths of Pain, more specifically Yahiko with the piercings fit the appearence of an antagonist best in my opinion. He was also immensely powerful able to destroy Konoha all by himself and was a serious threat to Naruto and the ninja world. At the same time, he was quite the foil for Naruto; both being students of Jiraiya, both being considered the Child of the Prophecy and so on.
These are my choices. Good question and great thread!
