My favorite eras have to be Third Doctor through the Fifth Doctor. There is something inherently cool about the early 70's. Pertwee's era in the 70's being low tech high science and his adventures with UNIT and the Brig bring smiles to my face.
The Tom Baker years I found exciting because it was like watching a theater show on television. The adventure, the comedy, the performances. All spot on and unique.
The Davison years I correspond to the most. There is a sense of adventure and mystery to be had. There is a good sense of family about it with Nyssa, Tegan, Adric and Turlough. As well as a sense of tradgedy when one by one all Fivey's companions leave him. Which I found way more powerful than the overlong, drawn out departure of Amy and Rory.