I'm very big into "pick up and play" type games where you don't need to invest a ton of time into getting into the story or complicated mechanics and leveling up systems. So RPGs by and large are out for me besides the original Kingdom Hearts (even by KH2 I sort of I fell off of that series because of how flashy and over the top the combat was compared to the first, but the original is a masterpiece with how well balanced and easy to use the leveling up, magic etc. were while still having some really memorably challenging moments. )
My two favorite genres are 2D platformers and drop-block puzzle games. Not a lot of people talk about it, but I think the puzzle game "Lumines" might be my all time favorite game. It's basically an evolution on the Tetris formula and has some crazy good visuals, controls, and the perfect "easy to learn, difficult to master" mechanics. All the skins are based on different songs and each song has a running "timeline" that clears matching squares to the pace of the music, so the game is just as effective as a rythm game than as a puzzle game. It was a standout launch title for the PSP and besides Mario Kart 8 Deluxe is THE game I've logged the most hours on my Switch with bar none.
Other than that, I consider the original two SNES Donkey Kong Country games to be the absolute gold standard when it comes to 2D platformers. As good as the new DKC games have been the zoomed out camera mixed with the blatantly more boring villain designs just hold them back from true greatness for me. Justice for the Kremlings!
Other than that, Super Mario World, the original Roller Coaster Tycoon trilogy, the original Tony Hawk's Pro Skater, and the original Crash Bandicoot trilogy come to mind as all time greats for me. I'm also really partial to classic arcade games. Give me a good round of Galaga, Dig Dug, Robotron, Ms. Pac-Man, any CAPCOM beat-em-up, the list goes on. It's really frustrating that more modern arcades have pretty much exclusively phased out their classic coin-ops for the big flashy "E Ticket" versions of these games.