Aha!  Now the shoe is on the other foot.  Jpcc86 was ahead of you before this post, but you got all 4 of these correct. 

10) Portal 2?

Already appeared further down the list, and did that game feature an in-universe 2D platformer? You're close, though.

All wrong I'm afraid

Correct!

Added a bit to each:

14) In previous games in this series, triggering too many alarms (four) would insta-fail the level. Here it just summons a small army of guards; a side character remarks that "this isn't a video game"

13) One of this game's many emotional moments features an interesting take on a Gilbert and Sullivan song (from The Pirates of Penzance).

12) This 3D platformer also includes an in-universe 2D platformer starring one of the main game's supporting characters - a celebrity who often serves as comic relief.

11) A guy goes really far out of his way for a rematch in a 1v1 duel, but only succeeds in making things worse.

Donkey Kong 64. The arcade game Donkey Kong is playable in game. Cranky Kong is the original Donkey Kong.

That's the best I've got.

Huh, I guess this pattern is more common than I thought. I'll add a bit more to disambiguate.

#24

Shin Megami Tensei: Persona 4 (PS2)

Change YOY: -1

There are various different reasons why a game might end up on my top 50 list, but in the case of Persona 4, the biggest reason it's so high on my list are the characters and the relationships the game builds between them over the course of this very long journey. It always just felt like everything else in the game was there to facilitate the growth and development of these characters, from the story about solving a number of strange murders, to the weird parallel world accessed through TV screens where the inner demons of the characters come out to haunt and attack them. Fortunately, those characters and their relationships are so great that it all works to the game's benefit in the end.

If I'd had to level some complaints at the game, I'd say that some of the dungeons drudge on for far too long, considering how they are almost all randomly generated and consist mainly of dull, interchangeable corridors with nothing but battles to keep you engaged. If the battle system was more nuanced and interesting it might work, but now many of the dungeons start to heavily drag before you get even halfway through them. It's good then that everything else about the game is excellent, so those blemishes are ultimately easy to overlook.

Last chance for 16:

16) "Eight. Eight. Eight. Eight."

The broom closet ending was my favorite.

"What do you mean we never put the game on consoles?"

15) *picks flower petals* "I know my past. I don't know my past. I know my past. I don't know my past..."

It takes an earthquake for you to finally find the answer.

14) Gravity is nothing before the might of a horse.

Your special ability is to yell.

13) This game involves significantly more paddling than previous entries in the series.

12) Probably the worst one competetively, but I sure like it nonetheless.

14) Skyrim?

Making them easier still...

14) In previous games in this series, triggering too many alarms (four) would insta-fail the level. Here it just summons a small army of guards; a side character remarks that "this isn't a video game"

This game changed its original title because it conflicted with a movie starring Ashton Kutcher that came out in the same year. The new title is a synonym of the old one.

13) One of this game's many emotional moments features an interesting take on a Gilbert and Sullivan song (from The Pirates of Penzance).

The song is the Major General song, but this character changes it to suit his own race and profession. The character feels guilty about one of his past actions and works hard to atone for it.

Mass Effect 3

12) This 3D platformer also includes an in-universe 2D platformer starring one of the main game's supporting characters - a celebrity who often serves as comic relief.

This game added a competitive multiplayer mode, though most later games in the series don't feature it.

As a distraction from the main story you can take part in a series of arena battles against increasingly difficult enemies on one planet.

11) A guy goes really far out of his way for a rematch in a 1v1 duel, but only succeeds in making things worse.

This game was released as an exclusive for a console after that console's successor had already launched.