I'm glad to see a lot of underrated gems in this thread. I'm often branded as a heretic when I tell people my favorite genre is fantasy games yet I've never played an Elder Scrolls game. There's definitely an argument that can be made for Breath of the Wild being the greatest game of all time, but when it comes to my personal most favorite video game of all time, I keep coming back to Skies of Arcadia: Legends on the Nintendo Gamecube (as the nerds among you could have guessed from my avatar).
The game opens up with you taking control of a swashbuckling Air Pirate and his spunky gold-obsessed female companion as you raid an imperial skyship that just kidnapped a mysterious girl. You beat the snot out of the guards on board, corner the admiral in charge of the ship, are forced to fight his warbeast as he escapes, you rescue the girl and sail away victorious across the beautiful open fantasy skies of a fantastical world of floating islands and six moons. And that's just the first 20 minutes. It is far from perfect and has a lot of flaws but I keep coming back to this game like a favorite novel. The story is solid (if not a little plot-holey at times), the gameplay is fun, the battles are cinematic and over-the-top and it's just a comfy well-made classic JRPG.
Also Stardew Valley fucking slaps.