As others have said, start with Eccleston. (watching the old episodes for the first time now will make them seem dated, that and a chunk of them are missing)
Although I think Eccleston had some of the poorest episodes (Rose, and the Slitheen eps), he was a good Doctor. Shame he only did 1 series as it started getting consitantly good in series 2 & 3.
My favourite episodes: (bold are the particularly special ones)
Series 1:
The End of the World
Dalek
Parting of the Ways
Series 2:
The Girl in the Fireplace
The Impossible Planet/The Satan Pit (double ep storyline)
Love & Monsters
Series 3:
Smith & Jones
42
Blink
The Sound of Drums
Series 4:
The Doctor's Daughter
Silence in the Library/Forest of the Dead
The Stolen Earth
Specials:
Planet of the Dead
The Waters of Mars
Series 5:
The Eleventh Hour
Amy's Choice
The Lodger
Series 6:
The Impossible Astronaut
The Rebel Flesh
Series 7:
The Doctor, the Widow & the Wardrobe
Asylum of the Daleks
Journey to the Centre of the TARDIS
The Name of the Doctor
