There is not a dud in the twelfth season (1974-1975):"Robot"
"The Ark in Space"
"The Sontaran Experiment"
"Genesis of the Daleks"
"Revenge of the Cybermen"
The twelfth season is the the Fourth Doctor's inaugural turn, features the first appearance of Davros, the origin of the Daleks, the best Sontaran story of the classic series, that goofy robot, a decent Cybermen, and probably the best humans living on a ship to preserve the species.
The Fourth Doctor's reign started on a very high note.
