#27: This flagship Wii title is one of the few Nintendo games that also released outside a Nintendo platform.

Nice. This is something I will now know until the end of time.

Another chance for #26.

#26
a) Dwarfs and elves on a hexfield.
b) Win with fewer turns to have more gold for the next level.
c) The game gets updates and additional content for over a decade now.
d) Control your armies one turn at a time.
e) Fight in a Tale of two brothers Under the burning Suns for The heir to the throne.
f) The Battle for ...
g) Download and play for free.

#25: Guessed by The_Liquid_Laser: Starcraft/Broodwar

#24
a) Control a red blob.
b) Eat PCB (printed circuit board).
c) Explode floppy disks.
d) Collect infotrons.

#23: Guessed by Landale_Star: The Legend of Zelda: Majora's Mask

#22
a) Gameplay switches between real-time strategy building up your bases and turn-based fights.
b) The real-time part presents you with the earth in globe view, with the possibility to rotate and zoom.

Second hint, it’s easy;

#27: This flagship Wii title is one of the few Nintendo games that also released outside a Nintendo platform.
Hint 2: And this happened earlier this year, though I think it’s only available in China.

Super Mario Galaxy.

This is a turn-based startegy game with units on a hexfield that you order to fulfill a mission. The gameplay is not unlike Fire Emblem games, but the setting and actual mechanics are different. You have to capture and defend villages in each mission, to gain gold to finance your troops. You can only bring units into battle, which you can pay for. You have different classes of units, each can level up, often with multiple advanced class-options. Different unit-types have different advantages or disadvantages against other unit types. The environment can give boni or mali. So for a mountain level you want to recruit dwarfs, for water levels merfolk.

The game can be downloaded completely free from the website. It is permanently developed on and new content gets added all the time. As this game is now more than a decade old you have a lot of main campaigns to choose from. In addition you can generate missions, play multiplayer or play user-created maps or campaigns. Give it a try, it is a great game.

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

Correct - nice one!

#26 was the Battle for Wesnoth, which nobody got. Better luck with the next games.

#25: Guessed by The_Liquid_Laser: Starcraft/Broodwar

#24: Guessed by OTBWY: Supaplex (Infotron is the Mac-port)

#23: Guessed by Landale_Star: The Legend of Zelda: Majora's Mask

#22
a) Gameplay switches between real-time strategy building up your bases and turn-based fights.
b) The real-time part presents you with the earth in globe view, with the possibility to rotate and zoom.
c) Recruit your soldiers from all over the world.

#21
a) This entry of the long going series actually sold the most.

#24 is Infotron.

https://www.youtube.com/watch?v=c24YTkn7K1w

Hehe, I actually never heard of Infotron. The video shows it is the game I have in mind. So a quick look at Wikipedia... yes, Infotron was the Mac-port of Supaplex, the game I meant. Seemingly music and maybe some level design was changed. But yeah, as it is a port, I give it to you.

https://www.youtube.com/watch?v=_11GaFZXdEA