Top 5:
1. Smash Ultimate
2. TES III: Morrowind
3. Heroes of Might and Magic III
4. FTL: Faster than Light
5. Warcraft III + Frozen Throne

Other games I think are great:
Divinity: Original Sin 2
Risk of Rain
Slay the Spire
Age of Wonders III
Baldur's Gate 2
Enter the Gungeon
Sunless Sea
The Banner Saga
Deep Rock Galactic

Perfect Games (via Steam Achievements, not necessarily 100%):
Risk of Rain
Subnautica
Into the Breach
Slay the Spire
Druidstone: The Secret of the Menhir Forest

:)