Probably Final Fantasy VI. (III when it was first released here in the US)

A serious and imaginative story, amazing art, memorable and interesting characters who had to make hard (and sometimes heartbreaking) decisions, and a huge world full of secrets and adventures to explore — that (spoiler warning) halfway through the game is essentially destroyed. I was in disbelief after the floating continent and ruin section - absolutely audacious. And it all comes together beautifully.

In the modern era, I would say Bloodborne. It so perfectly and completely achieves exactly what it sets out to do in gameplay, storytelling, and art that it sort of demotes every game to a lesser plane, even Elden Ring, which I loved.