When watching old Dr. Who, it is important to remember that they were extremely low-budget weekly serials. So special effects, details, continuity, etc. all suffered as the episodes had to be made very quickly. So it was all about the ideas, plot development, feeding the imagination, unique characters, and the quirky acting by the Doctor.

Also, the pacing was indeed much, MUCH slower than by today's standards, and stories were drawn out sometimes over 4 weeks, even up to 8 weeks. That's how movies and shows were back then. It's one of the things I enjoy about the old shows, you could really get immersed in a story over a long period of time, and really get to know the characters. Even now, if I watch an old story, I try and watch one installment, then a couple of days later, watch the next installment, etc., instead of bang-bang and its over in an hour.

Of the classic episodes, some of my favorites are "Talons of Weng Chang", "Genesis of the Daleks" (which has probably the best climax of any Who episode ever), and "Remembrance of the Daleks". I like the modern episodes too -- "Blink" blew me away. Although some of them are too melodramatic.