4. Inferno (Third Doctor)
Wow. Just wow. Many people (especially fans of NuWho) are often intimidated by the length of the Classic Series of Doctor Who. The average story was four episode 25 minutes apiece. But this one can strike fear into the hearts of new fans. A staggering 7 episodes chronicling the third Doctor's accidental journey into a parallel universe is not only awe-inspiring, but also worthy of your time, regardless of how much or little you like the classic series. It's aided by near-constant shifts in the plot. Nearly each of the seven episodes features a different story, all centered around the Doctor inside a drilling facility in a parallel universe, where everyone he knows is now his enemy. I really don't want to go into the plot more for fear of giving too much away. Just watch it. You won't regret it.
3. Genesis Of The Daleks (Fourth Doctor)
Coming in just one episode shorter than Inferno with six episodes, this is another epic must-see story for any fan of Doctor Who. The Time Lords temporarily rescind their order of non-interference in order to send the Doctor to witness the birth of the Daleks, and if possible, kill them all before they become the worst plague the universe has ever known When the Doctor arrives, he first tries to reason with their creator Davros, warning him of what the Daleks will become. https://www.youtube.com/watch?v=dkelV2WUNdw Finally, the Doctor is presented with an opportunity to do the deed himself. Which raises the question: Does he have the right? Would doing this - wiping out the entire race - make him just as bad, or even worse than the Daleks themselves?