The Brain of Morbius (Fourth Doctor).
An interesting take on Frankenstein but I think Terrence Dick's original concept of the lone robot trying to built a body for its master out of the spare parts it finds would have been more interesting. It's too bad the budget wasn't there. It also would have been interesting to expand upon Morbius' backstory. All we know is that he was a meglomaniac with millions of followers who destroyed civilizations.
The Seeds of Doom (Fourth Doctor).
I enjoyed this one but I kind of wish it had taken place exclusively in Antarctica. The claustrophobic feeling of being trapped with the Krynoid thousands of mile from any help. Then again I've just described John W. Campbell Jr.'s story 'Who Goes There?' and its various adaptations. It was also too bad that none of the familiar UNIT faces showed up this time around.