This should probably be in the cross over section, but considering how small that section is (20 fics) I'm going to take my chances here.
I wrote this to settle a debate among friends of who (out of Gandalf and the Doctor) is better.
Warning, this list is somewhat… ridiculous. It has the Doctor acting like a player, a couple ASOIAF references, as well as Gandalf and the Doctor literally comparing dick length. Please take it lightheartedly, as it is not meant as a reasonable argument.
Fifty three reasons why the Doctor would win in a fight against Gandalf, or just wins over him in general.
1. The Doctor has managed to tempt no less than 35 different women to come into his TARDIS in the space of eleven seasons. These have been his companions, not just visitors. Gandalf travels in a party exclusively filled with men. The adventurers in The Hobbit and The Lord of the Rings were all exclusively bro's.
2. One of those women was Kylie Minogue (2007 episode "Voyage of the Damned"). Generally, she is agreed to be a very attractive woman by the members of the human race.
3. You could argue that Gandalf is better because he has a wizard staff. Well, the Doctor has a wizard staff, too. It's called the Sonic Screwdriver.
4. The Doctor is able to just use his ability to talk at things to get out of pretty much any situation. He wouldn't have even had to fight Saruman, he would have just talked at him for five minutes and the white wizard would turn his tail and run.
5. The Doctor can use cups of tea as a weapon against his enemies, as he (being British) has an unlimited quantity of those stored in his TARDIS.
6. His TARDIS also technically counts as a woman, (Episode with the Eleventh Doctor "The Doctor's Wife) who the Doctor actually lives inside. Does that technically qualify as him having sex constantly throughout the day? I think so. 36.
7. The Doctor gets called 'sexy' by women around him frequently. Even Galadriel would back down if asked to call Gandalf that.
8. Gandalf must spend hours each morning getting his hair so completely straight, ready to go outside as the white wizard. While the Doctor, on the other hand, goes for a just-got-out-of-bed-in-the-morning look.
9. The Doctor's Sonic Screwdriver can unlock doors. Gandalf couldn't even figure out how to speak friend and enter, he needed Frodo's help in figuring it out.
10. The Doctor brings the mother of his wife, Amy, around with him all the time, and still hits on her almost 24/7.
11. The Doctor doesn't do drugs, they would damage his much needed brain cells.
12. While Gandalf spends his time stoning with Bilbo, the Doctor does important space work.
13. Gandalf has saved Middle Earth once, with a lot of help from his buddies in the Fellowship. Twice if you count Smaug as a threat to Middle Earth. The Doctor saves not just the Planet Earth, but the entire Universe every episode.
14. The Doctor had a scarf, once.
15. The Doctor has to wear suspenders as well as a bow tie, and completely rocks them.
16. Gandalf is probably going commando underneath those wizard robes. Even though that is a good thing, it would leave him very vulnerable in a fight.
17. Gandalf's wizard staff is longer and wider than the Doctor's Sonic, and yet the Doctor still gets more women than him.
18. If, in the case of a fight, the Doctor did get killed by Gandalf, he would just regenerate and get back into it straight away. While Gandalf did regenerate once, it took him a hell of a long time.
19. The Doctor has an ID in his wallet that he can show to you, and it will say whatever he wants it to. Not only that, but whoever sees it will instantly believe it. That means he could pretend to be Gandalf, and no one would know the difference.
20. There are Christmas specials for the Doctor, which shows that he has no problem in "getting merry."
21. Gandalf's wizard hat may have been one of the best hats in Fantasy, but the Doctor, in the eleventh incarnation alone, wore a top hat and fez. And rocked them.
22. The Doctor is pretty much, essentially, an immortal space pimp. Gandalf isn't a pimp of any calibre. (The multiple hats go as proof of that).
23. The Doctor is married, but no one is going to know about a little extra on the side (Oswin Oswalds), as he travels alone. If Gandalf tries to get down and dirty, the entire Fellowship will be able to hear the noise coming from his tent.
24. The Doctor had an annoying space robot dog following him around for a few seasons, and did not give a fuck. Gandalf would probably blow K9 to pieces by the second episode.
25. The Doctor managed to talk down an entire attacking starship of Daleks using nothing more than a Jammy Dodger. (British cookie. No, I'm not even joking.)
26. If Captain Kirk met the Doctor, they would probably team up and have the best bromance in all science fiction fantasy history. If Captain Kirk went to Middle Earth, he would probably become insanely bored with the lack of girls to get with and leave – despite Gandalf's best attempts to befriend him.
27. If Captain Picard met the Doctor, the Doctor would probably just pack up and leave, without even saying goodbye, due to Picard's incredible lameness. If Captain Picard met Gandalf, he would stay in Middle Earth for a long time, smoke with Gandalf, and engage in sexual relations with Elrond.
28. The Doctor has two hearts, so the blood technically should be able to pump oxygen around his muscles more quickly, so he should be able to run twice as fast as his human companions. He just doesn't, because he knows that the monsters chasing him don't have a fucking chance of ever getting to him.
29. Gandalf called the Fellowship "you fools!" during "Fly, you fools!". The Doctor would never directly insult his friends like that. But he would behind their backs.
30. When the Doctor insults you behind your back, you never find out.
31. The Doctor blew up the entire universe. The biggest quantity of fire Gandalf has ever made was started with pine-cones.
32. Gandalf probably had something going on with the Eagles, come to think of it. The Doctor never had to result to beastialty, he had enough ladies to hit on already in the TARDIS.
33. No one in all of the Lord of the Rings or the Hobbit was as annoying as Rory in the seasons with the Eleventh Doctor. But still, the Doctor put up with him without giving a single fuck, where Gandalf lashed out at Pippin quite a lot for looking into the palantír during "The Two Towers".
34. The Doctor has so many women running after him, that he actually discourages Amy Pond's affections, and hitches her to the hideous troll of a human being; Rory.
35. Gandalf just calls it quits and calls the Eagles when shit starts to get serious.
36. The Doctor never gives up, and if he fails, he just goes the heck back in time and fixes everything.
37. Frodo once offered to give Gandalf the Ring, and he declined it. The Doctor would never decline an extra bit of pimp jewellery.
38. Gandalf can speak the language of moths and butterflies. The Doctor can speak the language of dinosaurs and minotaurs.
39. The Doctor is such a worth foe throughout time that his enemies actually evolve to be able to defeat him.
40. The Daleks can go up stairs, they're just too afraid of the Doctor, who is standing at the top, so they pretend not to be able.
41. The Doctor is probably a member of House Lannister.
42. Gandalf is probably a Tyrell or Tully.
43. The Doctor can make children cry on Christmas.
44. The magic of children crying on Christmas can somehow be used to resurrect one of the Doctor's girlfriends – just like in the movie Ted, which was an excellent goddamn movie to say the least.
45. Gandalf's title is technically "Loremaster" which suggests that he knows a lot of Lore. He probably gleamed all that knowledge from reading. The Doctor doesn't waste his time with reading, he already knows every fact there is in the universe.
46. Gandalf fought against a group of wolves and goblins. The Doctor fought against a deadly crack in a little girl's wall. He doesn't even need to fight logical enemies.
47. The Doctor's favourite food is fish fingers. The manliest food Gandalf ever ate was probably something served up by The Prancing Pony. Yes, a place called The Prancing Pony.
48. The Doctor has fought more than 107 different types of enemies in all his adventures. Gandalf probably fought about 30, tops.
49. Even though Gandalf is really goddamn old, the Doctor is over a thousand, so he has more wisdom and experience.
50. The Doctor didn't need a beard to contain his awesomeness.
51. If you have sex while on the TARDIS, your baby will get turned into an immortal Time Lord (River Song is testament to that), even if it is with a human. Your baby will become an all knowing god.
52. If you have sex while in Rivendell, you will just get a bunch of elves staring at you judgementally.
53. The Doctor kissed a man, (episode 12 of the sixth season), and no one ever found out about it.