#18 - The Triforce Cup is a DLC.

Nope, not even close :(. I will say though, that this game is on the same system as 3 early entries in Romance of the Three Kingdoms.

16. A guy and a girl battle against an ogre queen and a weapons merchant trying to drum up a global war.
Hint #2: The girl's mom is the ogre queen while the weapons merchant is the guy's brother (sort of).

I'll drop a couple of hints for my next few:

#17 - An indie roguelike dungeon-crawler with incredible depth, including a job system, pets, and a meaty campaign that takes you through a bunch of randomly generated dungeons.

#16 - A gaming icon's first foray into RPGs. With an intricately crafted world and great characters, it stands the test of time today.

#15 - Culinary chaos.

Uhm, Mario Kart 8.

#17: nethack

#16: Super Mario RPG: Legend of the Seven Stars

#15: Overcooked

More clues:

15. a) The developer of this game actually created another successful series first.  But then the developers and their publisher were bought by two different companies.  That lead this developer to create this game which had the developer's first series as their main competitor.
b)  The publisher of the first series made plastic instruments.  But I am looking for the first game in the second series.

14. a) This fantasy beat'em up lets you choose from 3 different characters.
b) Sega

13.  a)  One way this spiritual successor changed from it's previous game is that it was no longer a PS3 exclusive.
b)  Your ability to level up and buy equipment come from the same "currency".

15. Uh, that is Rock Band.

EDIT:

#13: And that is Dark Souls.

I played Supaplex a lot back in the day. Solving one more level or retry after failing was a very addictive loop. This game in it's core is a Boulderdash-clone, but added some things and had such neat artstyle and sound-design.

As in Boulderdash you go through the level, collecting (in this case) Infotrons and avoid being hit by a stones. The game includes exploding floppy disks, enemies (the scissors you see above), gravity for some levels and some other stuff to keep it fresh. Overall it contains 111 levels, but if one level is too difficult, you can skip it, but the number of skips is limited.

The game released originally for Amiga and DOS. But it got many clones and rereleases like Megaplex for Windows (with level editor), Infotron for MacOS, Igor The Time Machine (an extended game from the same devs), WinPlex, New Supaplex, Supaplex 3000 and an adapation for the Apple Appstore. If you want to play it, you have certainly a lot of options. For the original feeling, download it from the developers and play it in DosBox.

https://www.youtube.com/watch?v=K5M4bVJZYPI

Starcraft is a historic game. It mixed the formula for real time strategy in a way, which was wildly successful. It was also the game, that spawned e-Sport leagues starting in Korea. It was a mainstay in LAN-parties for more than a decade. The included map editor created a lively online community sharing new creations. Blizzard supported that by releasing the Map of the Month for a long time. Among the user creations were maps that started the Tower Defense genre. Blizzard introduced the expansion Brood War, which added a lot of content and kept the game alive for even longer. I think it is fair to say, that the gaming world today would look different without StarCraft.

This game was a lot of fun to play. At college a group of friends often met to play StarCraft matches locally in the LAN. And without them I played the single player campaign. Which was doubled by Brood War.

The game has a sci-fi setting with three warring civilizations, humans and the alien races of Zerg and Protoss. Each faction has their own research tree, own units and specialties. Again, reasearch and unit types were extended by the excellent Brood War expansion.

By the way, it is unintentional that now for the third year StarCraft ranks #25. I make the lists new each time, and other games jumped around quite a bit. So it is kinda funny StarCraft is stuck exactly in the middle of my list.

If you want to play it today, you can download the original game (well, with a lot of patches that came over the years) for free from Blizzard, or you can purchase the remastered version. Either way, it is a great classic game.

https://www.youtube.com/watch?v=-00uQzXyujI

One of the oldest gaming series that exists, is the adventure series Zork. This series started 1977 on a PDP and was 1980 transformed into the Zork series by the company founded for this purpose, Infocom. The games back then were text adventures, meaning everything was text, you typed in your command and on the screen was shown text that described the result. Zork was for the time an incredibly successful game (for the time) and Infocom was among the greatest gaming companies. But the failure of a Lotus Notes clone (which itself was overtaken by Excel later) and the introduction of graphical adventures by different companies led to financial trouble for Infocom, and it was taken over by Activision. Activision tried to make money of their Zork-franchise they've gotten through this aquisition and as a result developed Return to Zork.

Return to Zork was the first graphical adventure in the Zork series, but it was also very unique in it's way. For starters the game used real actors and integrated these videos instead of animated sprites. This was used by other games at the time, but Activision actually took care that these scenes meshed well with the painted backgrounds, so that the video captures don't stick out. They also had a very interesting point-and-click interface. They didn't follow the standard set by LucasArts (Indiana Jones/Monkey Island) and Sierra (Kings/Space quest/Larry) games, but instead opened a graphical menu if you clicked on any interactive element in the graphic. You also could 'hold' an item in your inventory and then click, and the menu offered a lot of ways to use the item on the interactive element. This way the game retained some of the depth of the text adventures (which allowed for a lot of interactive possibilities). This and humorous flashbacks to the older games in the series (like in the image above) was made to draw in old fans.

In difference to more puzzle oriented adventures, Return to Zork has a good cast of characters which you can interact with. There are a lot of communication options, including asking about photographs you've taken from different locations or characters, audiologs or places on the map. Additionally you have a magical orb and the wizard communicating through it has a lot of comments to different situations.

This game shows a lot of possibilities for developing an adventure, which I seldomly saw used in other games. It also has an interesting story, a variety of characters and brain-teasing puzzles. In this game you can die or make choices that lead to make the game unwinnable, but the game always instantly tells you that, so that you can go back to the last safe situation.

If you wanna play the game today, you can purchase it from GOG, play it in the browser at archive.org or reuse your old copy with DosBox. A fan of point-and-click adventures should possibly give it a try.

https://www.youtube.com/watch?v=kx5F8zra5zs