1. the third was a very good fighter. Plus, hiruzen died, orochimaru didn't. Common sense says that orochimaru was closer to winning.
2. orochimaru was sick, had decaying arms and was desperate to be healed. He was usually sick, but a healthy orochimaru is deadlier.

3. two reasons: this was a show-off of the 4th tail's awesomeness

, and in that state naruto was impenetrable. Orochimaru had no innate abilities to control a biju, like yamato does. And he wasn't really defeated. They were two thick shells bouncing into one another. this fight could have dragged on forever.
I'm not implying that orochimaru is invincible (in his healthy state), but few people could beat him. Sasuke was not stronger than orochimaru. He just got lucky and found him half-dead.