They say you can never forget your first Doctor. If any of the many actors who have played The Doctor since Dr. Who's premier in 1963 deserves the honour of being your first it is absolutely Christopher Eccleston, a gifted actor whose work you probably know already even if you never connected his name to his diverse roles.
Eccleston only played The Doctor for this single season; he did not renew his contract. But his work here sets the ground work for every Dr. Who episode created since. Gone is the absent-minded professor type of the first eight Doctors. Eccleston's Doctor is thoughtful, direct, and action-focused. This is a Time Lord with a plan who doesn't hesitate to do whatever needs to be done and has both the knowledge and experience to solve problems that would confuse others.
He is also a haunted man, regenerating out of the War Doctor (see "Day of the Doctor" from the 50th anniversary specials), the sole survivor of the Great Time War, his conscience thick with the horrors of that war and his role in it, a conscience that makes him more determined than ever to help others -- starting with Rose Tyler in the first episode, "Rose."
This journey with the Ninth Doctor is far too short, our time with him feeling like the blink of an eye. But we are better for meeting Christopher Eccleston's Doctor on this journey of discover that will make you laugh, cry, and cheer.