(Kalinara started a meme.)
1) Continuity Porn -- Yes, I am that kind of fan. The one that DC caters to. The one that keeps Geoff Johns in the job. The one who perfectly satisfied to read five different versions of the exact same story, published at different time periods and adjusted for continuity.
2) Time travel storylines, guest-starring the Legion of Superheroes from any publishing period.
3) Any version of Starman, because of the intricate history James Robinson set up.
4) That every Flash who has ever been published can team up to fight a single villain.
5) Power Girl's playful banter with Wildcat reminds me of me and the guys at work.
7) She-Hulk enjoys her super-strong green form.
8) The core team of the JSA is essentially a bunch of cranky old men who probably get together with old supervillains to play poker.
9) Characters I love who died (Ice) can be brought back to life. Characters I love who went evil can always have been mind-controlled.
10) John Stewart's first appearance when he steps in between the cops and the checker-playing kids.
11) Retroactive Continuity!!
12) I've been following these characters long enough to be able to fill in the spaces between the panels.
13) Quicksilver is an absolute jerk when he's good. He can also believably go insane and evil and I still adore the character.
14) Patrick Gleason's aliens.
15) Somewhere in the Multiverse there is an Earth controlled by Nazi Dinosaurs.
16) Multi-part serial stories which give me something to think about as I do mindless repetitive tasks.
17) Green Lantern's powers have as much visual potential as an illusionist, but all entirely in my favorite color.
18) I can read about both Kyle and Hal.
19) Spider-man interacts playfully with random New Yorkers.
20) Big Barda is the muscular ass-kicker in the Free family, and Scott isn't the least bit bothered by this.
21) A large percentage of the male population of Opal City wear fedoras.
22) Black Canary was still a hero when she lost her powers.
23) Manhunter is divorced. She is not a castrating bitch. Her husband is not deadbeat Dad. They are two decent people who couldn't make it work out, and there was no need to make anyone the villain to make the other look better.
24) The original Red Tornado was just a lady with a pot over her head and a blanket-cape, even came from a humor book, but in the modern DCU she's known as a hero and her flashback stories drive that home.
25) Tim Drake and Maxine Hunkle are overenthusiastic hero-worshippers who became heroes.
26) "When I'm no longer needed to battle crime and injustice" is a better answer to "When will you marry me?" than "When Hell freezes over"
27) It is almost completely random, yet very funny, that panels featuring Green Lantern are usually a rear-view.
28) Whatever damage is done by the current writer can be fixed by the next writer's retcon, reboot, or just plain redemptive writing.
29) That even the tropes I despise are so well-known that we have a staple of jokes to make when we see them. (Yes, I love Fridge jokes. Surely you all knew that)
30) The term "cosmic rod" makes me giggle like a 12-year-old.
31) Husk can shed skin like a snake.
32) Mutants like Domino, Longshot, and Scarlet Witch, who have vague probability powers that conform to the writer's needs.
33) Shining Knight is a teenaged girl with a sword, gold armor, an Arthurian history, and a flying horse!
34) The cover to Defenders #5 has a giant monster holding a blonde woman in his hand just like King Kong -- only this woman is swinging a sword at the monster! (And she's a valkyrie!)
35) Wonder Woman killed Medusa on live television, while she was wide awake. Touch that, Perseus!
36) Lois Lane is a driven, pushy, arrogant, complaining, sneaky modern career woman. As a result, she gets to see Superman with his briefs off on a regular basis.
37) Captain Comet still appears from time to time.
38) All Brainiacs are pretty much dicks, whatever time period and moral alignment they show up in.
39) Grant Morrison.
40) No knockoff can hold up to the original Superman.
41) You can make an easy Jack Knight costume for any convention with a pair of boxers, a Hawaiian shirt, a leather jacket, ski goggles, and a broomstick that's been spray-painted gold.
42) The industry pros are part of the fandom.
43) The creepy visual effect of shadow powers when the Shade, Obsidian, or Nightshade show up.
44) That Blink was so popular after Age of Apocalypse she was the anchor for a new series.
45) Kyle Rayner, in the alley, with the lead pipe.
46) Everything is just so much bigger in the DC and Marvel Universes. The stakes are higher for everything. Aliens invade every week. The End of the World is nigh every month. People don't just have fist-fights, they have aerial battles over the mountains while the government calls out the Air Force to take out the winner.
47) At the same time, there's street heroes who handle normal crime and everyday accidents. They interact with the cosmic-level heroes and team-up.
48) Science Fiction, Fantasy, Mystery, and Romance genre stories all take place in the same city.
49) "You made me lose my hair!" was not the motivation for a female villain.
50) The story where Power Girl lifts up an Arthurian-era knight and throws him into a lake after he tries to run off with her per the laws of Chivalry? Collected in trade now.