Zelda: Oracle of Seasons (GBC)
Runner up: Pokemon gold/silver (GBC)

Metroid Fusion was a banger. I didn't even own a Gameboy, but my friend did, and I would trade him half my allowance every week to let me borrow it over the weekend. Many many nights were spent up late under the covers exploring BSL Station.

GBA Yoshi's Island, legit had the hooks in me for years

That and Sonic Advanced

The first game I bought for the Nintendo DS was Trauma Center. It really sold me on the idea that new kinds of games were possible with the touch screen and stylus. It was also extremely challenging to get the highest rank on each stage. I spent hours playing the stages over and over trying to get the top ranks. The arcade style gameplay was pretty addictive, and it had a good storyline too.

It's a tie between Pikmin 4 and Breath of The Wild, I love Pikmin and think about it a lot. Probably broke a world record with how fast I unpacked that game and slid it into my Switch!

Even though I've 100% completed the game 7 times, I still come back to this track, I love the vibe, gives me summer BBQ day feels!

Breath of the Wild is a game I really would love to play again as if it were new, it gave me such a sense of adventure and desolation that no other game has achieved. I'll sometimes boot it up just to lie down and relax to it

Metal Gear Solid: Peace Walker for the PSP was pretty great.

Gonna go with Donkey Kong (1994). Made for a handheld (Game Boy) but also prominently features an enhanced mode enabled by running it on Nintendo's Super Game Boy accessory for the SNES/Super Famicom (actually mine's an SGB2–even better).

Phantasy Star Portable on the PSP was really good, I think I wore out my thumbstick playing it.

I think the Zelda Oracle games were pretty rad. Easy games to play, and for the truly committed you had cross progression between the two games to complete quests across Seasons and Ages. The two games had completely different maps and dungeons to explore with different items in each. They were a dual release that weren't just the same maps with slightly reshuffled enemies like the Pokémon games were. I remember trading my copy of Seasons to my friend for his copy of Ages and then checking in with each other to see where we were and if either of us had discovered any secrets that we hadn't found in our respective playthrough.

Boktai 2: Solar Boy Django. You play a vampire hunter with a solar powered gun, and the gimmick is that the GBA cartridge contains a UV sensor so that you're required to go outside and use real sunlight. It's such an absurd gimmick, but it works. It works incredibly well and makes it an unforgettable experience.

The first game is alright, but the second is where the series really came into its own.

Jeanne D'arc on PSP has to be the best tactical rpg I've played for pure fun value amazingly polished game if not that well known.

PSP has an amazing catalog I still keep a ton of them on my phone and attach a bluetooth controller.

Dude playing MHFU on PSP with friends was literally peak gaming!

You mean like fully intended to make use of a handheld? Maybe Pokemon Platinum or spectrobes. I haven't played very many mobile first games, most games I've played on switch or even the ds would work perfectly fine on another system.

If we're talking games that are just on the switch first, then probably neon white. The gyroscope is surprisingly good for shooting, i thought it'd get annoying but it didn't.

But of course i think Catherine is one of the switch's biggest must plays.

Castlevania: Circle of the Moon (GBA). Being able to grind XP / gear to compensate for my bad platforming skills was amazing. Also this sparked my love for Metroidvania games.

As a member of the original Game Boy generation who had a much-loved stack of carts for the old brick, I feel a bit basic saying the packed-in Tetris was my favorite one but it really was the one I kept going back to for a quick fix.

I also really adored Final Fantasy Adventure (a.k.a. Seiken Densetsu or Mystic Quest) but that was never a quick fix, that was one for sitting down with for a properly long ARPG session.

I just got a handheld emulation machine that runs pretty much anything up to Dreamcast, and having a huge chunk of the history of gaming in my pocket has been rad as hell.

Rediscovering a lot of GBA games has been a lot of fun. Wario Land 4 is so fucking good, and I feel like it's been completely forgotten.

Phantom Hourglass and Spirit Tracks were pretty cool. I played both with the stylus because the DS control pad is tiny as fuck, literally painful to use for more than a few minutes.

Same with the Layton games.

I love Tearaway on Vita. Very creative use of all the handheld’s features (cameras, touch screen, rear touchpad, microphone, motion). The best bit is seeing your fingers bursting through the back and into the screen. The PS4 version of the game really shows how disappointing it is not to play on the Vita, even with vastly improved hardware.

Do mobile games count?

BotW hands down, but Pokemon Emerald is always a great option for emulators. Or any Fire Emblem game.

half minute hero. the section where you have the duel greaves has lived with me every day of my life.

I don't think there was a marriage between a game and a system as perfect as with The World Ends With You and the original DS.

The game has been rereleased on multiple platforms since then. And yet it's nearly universally accepted that if you can play in on the DS/3DS, you should.

For instance, one of the main themes of the game is that you can't do everything on your own, so you need to trust and work with other people. And so, TWEWY uses both of the console's screens and makes you battle with both the protagonist and his partner at the same time — a very unique system.

It works even better on the DS, because the stylus gives you the much needed precision even on an otherwise unimpressive touch screen. This is one of the main reasons the original just plays much better than the ports.

The game also tells you to expand your world by interacting with others — and implements a rudimentary StreetPass-like feature, several years before the actual StreetPass, that rewards you for meeting other people in real life.

Along the same lines, it encourages you not to spend all the time playing it. So another type of reward you can receive basically requires you to turn the game off and go touch grass.

It also has an interesting food mechanic, that only allows you to eat a couple of heavy dishes per a real world day. You can snack all you want, but the only way to raise Attack and Defense are the big food pieces. So you'll have an easier time if you take your time with the game, take breaks and properly raise these stats, although that's by no means required.

Of course, it also uses the console's other features in more conventional ways. Some of the attacks you can use, for example, utilize the microphone, and one mini-boss requires you to put the console to sleep.

And yeah, it's just a super cool game overall. Many enthusiasts consider it to be the best on the system. Amazing gameplay with tons of variety, great plot, fun characters, really good postgame to sink hours into.

Gotta be Mario's Picross fo sho

I'm not sure if I would stick to this pick given more thought but Donkey Kong '94 first came to mind.