4. Series 3
When Series 3 first released, it earned a lot of bad reviews because fans disliked Martha's character, especially when compared with Billie Piper's Rose. However, this initial distaste has lessened over the years, as fans can't deny that Series 3 has some of the best episodes in Doctor Who history.
While episodes three through seven are pretty average quality, there's a lot to love about the rest of the season. "Human Nature" and "The Family of Blood" have been held up as some of David Tennant's best performances, and "Blink" is still the highest-rated episode on IMDb, with a score of 9.8/10.
In addition, the three-part season finale is elegantly crafted, tying together plot threads from earlier in the season and giving Martha the chance to show how strong she is. John Simm does an amazing job as the Master, and the finale even completes Jack's Season 1 arc from Torchwood.
Series 3 might not have had the romantic chemistry of the first two seasons, but it included individual episodes and season-long arcs that deserve recognition. It's definitely a season that long-time fans should take the time to rewatch, because it holds up much better than anybody could have guessed when it first aired.