3. The Stolen Earth/Journey's End
The great culmination of the genius of Russell T. Davies as the season concludes. I love it for so many reasons - big sets, planets being yanked out of time and space - the whole gang - all our favorite faces - are back and out to defeat the Daleks, who've hatched a diabolical plan to wipe out reality itself and obliterate everything to nothing. The Doctor can only watch as the Tardis is being destroyed with Donna inside, his Children of Time want to kill for him and hope is fading fast. Yet then, a new Doctor appears, one grown from the hand cut off while regenerating on Christmas Day and Donna! The Doctor/Donna get the job done; the universe, once again, is safe, but at a high cost to Donna. There cannot be a human/Time Lord metacrisis; the Doctor wipes her mind of all memories of their adventures, meaning that if she remembers, she will burn up and die. After all that, the Doctor loses Donna and Rose and ends up alone. Everyone else gets a happy ending, especially Rose; she gets to keep the new Doctor, who is human, therefore, can grow old with her.
The Questions: Would you rather have lived and loved and felt the pain of loss? Or never have loved at all?