Heroes of Might & Magic II

You sir have excellent taste in games.  This would be my #2 pick.

My top pick is The Legend of Zelda (NES).  This was my most played game back in the NES era (although SMB and FF1 both got a lot of playtime too).  The combination of great action, tight controls, and perfect challenge level combined with the open world, the NPC's, the character progression and all of the other RPG tropes from the 80's meant I just loved coming back to Hyrule and specifically this version of Hyrule above all of the others.

Many years later I came back to Zelda 1 on the Virtual Console and found the game was even more fun than before.  It has aged like wine.  I still haven't found a game since that has the perfect combination of tight controls, intense combat, good challenge, exploration and immersion into a fantasy game world.  The closest I've seen, I think, is Elden Ring, and even then Elden Ring doesn't have as good controls and it's challenge factor is very uneven throughout the game.  Zelda 1 is just perfect.

Darkest Dungeon then Diablo II then Yoshi's Island

My pick is potentially Hollow Knight. It is a genuine masterpiece to the extent I enjoyed replaying it last year even more than I did playing Silksong.

Super Mario World and A Link to the Past are near the top of my list as well, as both near perfected their genres.