RetroGaming

Wario Land 2 + 3 Were the first games I ever played on a Nintendo handheld. I still play them through once a year because of nostalgic reasons. Plus they are one of the most enjoyable Jump and Runs for me.

Ninja 5-0 for the GBA. I got out my collection recently and had no idea I owned it. It's Elevator Action, but you're a ninja.

God Medicine. Genuinely one of the best classic style JRPGs and the best RPG on Gameboy in my opinion. Absolute travesty that the west never ended up getting it originally.

Dragon Warrior Monsters.

I think I'm the only person who's beaten the Monster Master fight enough times to know there's a bug in it where he eventually gets strong enough that you get one shotted by him even if you're cheating and using a Gameshark to keep your health in the 1024 hp range...

Aside from a few classics I'm sure you've already played, I remember playing Wario Blast and Taz-Mania fairly often.

I haven't played either one in years, so I don't know how well they still hold up.

The Moomin game is great but nobody talks about it. The two Survival Kids games are incredible as well but damn they can be depressing. They really out a full on survival game on a Game Boy. Complete with multiple endings, open world and hunger and thirst mechanics.

Probably doesn't hold up anymore, but no one really talks about "Kingdom ~~Conquest~~ Crusade". It's like a really tight minimalist version of the combined live action melee and big battle strategy of the Dynasty Warriors series - compressed to fit on a classic Gameboy.

I had an Itchy and Scratchy game (from the Simpsons). It was a mini golf game that was a lot of fun.

Radar Mission. I can hear the music in my head from both game types whenever I think about it, right down to the music when the carrier launches the fighter. I enjoyed both game types a lot, though I remember getting frustrated as a kid until I learned the nuances of the opponents.

Cosmo Tank. Got it as a gift from my dad and loved it when I was a kid. I may have to revisit it myself.

Rebelstar: Tactical Command, In a nutshell it's X-COM for the gameboy advance.

Falling sand games, specter supreme, escape velocity, gyromite.

I didn’t have a Gameboy, but I did have an Atari Lynx and I would say for Atari it was Batman in color.

Quest for Camelot was a banger. I think it's in NSO actually. The sword swing sound effect is burned into my DNA.

You know what was great and gets no love? Q*Bert for GameBoy was a really solid game that had a LOT of stage variety and even silly cutscenes. Literally the only thing it was missing was color. Highly recommend.

Pac in Time was a great game, came bundle with my red original Game Boy. Turok 1 and 2 for Gameboy were loads of fun too

Vegas Stakes - simple casino games, perfect time-killer for the format.

Wendy Every Witch Way - concept of reversing gravity has been used in other platformers since, but this might be the OG, and is very solid.