The Ninth Doctor as an Echo of the First Doctor → 
Matthew Hyde on the ninth Doctor:
And so the 9th Doctor was damaged, and that’s how Eccleston played him, a man who could put on a goofy smile to mask anger, depression and bitterness. And yet that’s only a part of it – there was almost a sense that the Doctor was no longer happy with who he was. That’s why he dressed as a bloke from the pub – he was running from the trappings of being the Doctor, the hero who saved people from the monsters because, when it came down to it, he couldn’t save his own people – worse, he couldn’t save them and he was the one who pulled the trigger. That’s why the 9th Doctor needed an actor like Eccleston, someone who could sell the idea of a broken-down hero who was trying to be true to himself whilst being haunted by a war full of ghosts. And so his story arc was to find redemption – when faced with a near-identical situation to that which forced him to wipe out the Time Lords, he manages to win – sure, it’s because of his influence on a single individual rather than a grand plan, and it costs him his current incarnation in the process, but he wins – he wins and in doing so he fully becomes the Doctor again. […]
In many ways, the story of the 9th Doctor runs parallel to that of the first – someone who, as the TARDIS Eruditorum blog points out, had to learn how to be a hero in order for the show to move to its next stage. And to really sell that, you don’t need a leading man, you need a powerful, dedicated character actor who’ll take a role that tabloids feel should go to some random celebrity and bring the actor’s craft to bear. Get that and you get something special. And that’s why, when Christopher Eccleston delivers the 9th Doctor’s last words, it’s a real lump in the throat moment:
“Rose, before I go, I just want to tell you, you were fantastic, absolutely fantastic. And you know what? So was I.”
Both the first Doctor and ninth Doctor were very similar: men who could no longer return home (either by accident or by design), men who had few connections left to the universe, but men who loved to travel and discover. It was only through their death-through-regeneration did the Doctor rediscover their connection to the universe. They discovered their friends.