I remember Doctor Who from the 70's. Jon Pertwee was the first one that I have a good recollection of. I must confess, however, that I thought at the time(and still do) that those earlier episodes were absolutely rubbish. I certainly didn't mourn their passing when they were taken off the air.
I saw a couple of episodes of the rejuvenated series with Christopher Ecclestone and thought that they were okay. I really got into them when David Tennant took over the mantle. He, along with the great story lines, made this one of the best shows on tv in 2007. I was also pleasantly surprised by Billie Pipers performance. I have read that David Tennant is due to step down from the role and the new Doctor will be played by John Simms, who recently played 'The Master' in a few episodes.
David Tennant will be hard to beat though.
The resurrgence of the 'Doctor' has also spawned numerous toys, just in time for Christmas. My 4 year old has asked Santa for a 'sonic screwdriver'. I only hope that Santa watches Doctor Who!