Tom Baker is my favorite Doctor, and I am co-admin of a forum called Who On Earth Is Tom Baker
. But the Hartnell stories were wonderful, too - especially the historical ones. I highly recommend The Aztecs, in which the Doctor nearly finds himself getting married! (seems he didn't realize that offering a lady a cup of cocoa isn't quite so innocent in some cultures...
Richard Hurndall did a good job in The Five Doctors. I read somewhere that he played another role in a Doctor Who story previously, but don't recall which one.