The first point in this meme is "Favorite Series", and there's really no contest in my mind here: the best series of the modern Doctor Who is Series 4. Now, this series does not include my favorite episode or my favorite story arc, interestingly enough. I have a different set of criteria for what my favorite series would be.
First, Series 4's episodes have a high level of quality. There's not a single stinker episode in the entire run (there's no "Love and Monsters" or "In the Forest of the Night"), and all of them are enjoyable, even if some of them aren't exactly deep. "Partners in Crime" and "The Unicorn and the Wasp" are simply fun. Then we have some of the most meaningful episodes of the run: "The Fires of Pompeii", "Silence in the Library"/"Forest of the Dead", "Turn Left", and "The Stolen Earth"/"Journey's End". And of course, the episode that in my opinion is the best of the modern show (but is not my favorite because it is simply too horrifying to watch), "Midnight."
Then, of course, there's Donna. It would be very difficult to choose as my favorite series one that doesn't have my favorite companion. She was fantastic, and Catherine Tate was fantastic playing her. I've never really before understood what it meant when someone would say, "Those two have a great chemistry on screen," but with Tennant and Tate, I got it. They worked. They meshed. The series was good, but they made it shine.
Lastly, this is the series of the fully mature Tenth Doctor. He's not young and silly and foolish, following Rose around like a puppy, and he's not suffering the backlash of losing her by becoming callous toward Martha, taking her for granted. He's returned to his responsibilities as a Time Lord and as the Doctor, with Donna's guiding hand, and the stories reflected that, returning more to the classic style of the Doctor exploring the universe working with his companion to do brilliant things. The side stories of Donna's family and the introduction of River Song and the hidden plot of the Daleks added flavor and continuity, but this series is all about the Doctor growing into his own and facing the things about himself that he's ignored for too long.