About my 30-21:

30. Myst III: Exile (PC)

Best of the series in gameplay.

29. Halo: Combat Evolved (PC)

28. Indiana Jones and the Fate of Atlantis (PC)

Possibly best of the Lucas adventures in gameplay. I miss the time when "Indy 4" meant this.

27. Final Fantasy VI (SNES)

26. Full Throttle (PC)

Another beautiful Lucas adventure, with unique puzzles. Rather short and would be higher without that fighting bit.

25. Colin McRae Rally 2005 (PC)

While certain cars are horrible to drive, the game does so many things right.

24. Pokemon Crystal (GBC)

I've played four first generations and this was the peak.

23. Populous (SMS)

Master System pad is better controller for Populous than a mouse.

22. Dragon Strike (PC)

Dragon flight sim, use lance, sword, breath, claws... or land and let your dragon eat a few people!

21. Crush! Deluxe (PC)

Turn-based violent scifi sports strategy. More satisfying against two human players, the simple AI only wins by luck. But really wonderful game nevertheless.

#25: Let's try another one: Divinity: Original Sin... 2? I choose the second one, because more people seem to know it and it is generally very well liked.

#23: Metroid maybe? I think in Metroid II you have a baby Metroid companion, so I choose that.

Three of five had been guessed so only these two remain. Time for hint 2;

#17: This game ends with the raising of the Victory Banner on top of the enemy's government building, in reality one of the most iconic images ever.
Hint 2: The game series itself would become pretty iconic as well, within the sphere of video games anyway, a couple of successors later. Guessed by Mnementh - Call of Duty

#16: Even though the blue bartender in the cutscene isn't very helpful at first, when the protagonist shows his civilised weapon he's suddenly a bit more open about things.
Hint 2: This elegant weapon however is the wrong color for some reason. In this game it's blue, and it's supposed to be "yours", but in the previous game the weapon was green. At least using it is not clumsy.

UnderwaterFunktown overtook S.Peelman with now 4 guesses. Darashiva and Machina are still in the lead. See here.

Let's add some hints for the unguessed games:

#20: Baldur's Gate as guessed by Darashiva.

#19:
The game has some innovative ideas, mainly it tries it's hand at procedural story generation and character growth, meaning each playthrough is different.
First the Age of Ulstryx.

#18: Breath of the Wild as guessed by Darashiva.
Our boy needs a 100-year nap after losing a fight and the girl has to hold the fort for the time.

#17: (not Outer Wilds)
20 minute survivors.

#16:
"Sorry to keep you waiting!" ... does a simple sorry cut it, if the wait was 26 or 21 years (depending on the region)?

#17:

I didn't knew the original Call of Duty featured this:

Yep. Call of Duty is correct. Well, maybe not as dramatic as the real photo but the final level (without expansion pack) has you assaulting the Reichstag and make it to the roof where one of the NPC's places a flag.

EDIT:

Yeah definitely not as dramatic as the real thing.

Correct!

You wont get any cake however.

Well, almost correct on 25. Could have put any of the two Divinity original sin games. They feel very similar to me, prefer the first one still. 

Metroid is not correct however =)