Im actually glad the thread asked for more than one handheld instead of picking just one.
Because that would be a massive problem for me lol
I enjoy the generational jumps between devices soo
Tiger Electronics and similar games [learned a lot about how LCDs worked in this sense, as a kid this was fascinating]
Gameboy DMG [i tried figuring out how the device was doing any of what it was doing, i didn't have much of a grasp in tech as i was still a child that could just barely read english]
Gameboy Color [I still liked it but i was much more a Super Gameboy fan at this point]
Gameboy Advance [SNES in your pocket, that was the meme at the time... eh it was right mostly, the early gba games were a bit of a mess though but you can notice the improvements pretty quickly compared to other handhelds and even consoles]
Nintendo DS [The first system was great, didn't care much for the lite, the DSi was a worthy upgrade]
3DS [One of the biggest jumps imo, lots of tech that honestly wasn't really available to the general public that is suddenly right there in front of you, ARG-like elements with streetpass functionality I think this entire series was pretty great save for not being able to play GBA games. If a version of pokemon go came out for this, no one in their right mind would ever release a handheld device again. pokemon is the new crack]
PSVita [Biggest issue I had with the original PSP was that it only had one analog stick, i mean it worked for what it was but there could have been more going on with it. The Vita was what the original psp should have been. I haven't met many people who liked the Vita]
Pandora/Pyra [Wonderful learning experience, figuring out how things work and how to get stuff working on it is a rewarding experience, i mean its definitely not for everyone but for the people who stick around its like a valhalla, despite having other devices that can also play retro games, this device will be the DEFACTO way of playing older retro games. It was never about how much power you can fit in a handheld, its about efficiency and the battery life and device design points mark this as law. It'll be a while before another group makes a device that can reach similar battery life and portability without dumbing down the experience for advanced users ]
SteamDeck [just recently got this not long enough to make a formal review of the device but i really enjoy it so far. This is a major deal in several aspects, it can play stuff that i know the architecture for like the back of my hand that dictates no possible way to run it on AMD chipsets. SunsetOverdrive for those wondering btw was built in such a way that for a while the PC version would only run on intel hardware. It was an insane surprise. Personally, from the few days ive had mine, i wouldn't really recommend it for the general user namely those unwilling to tinker with their devices, there is a lot more going on in this device besides the ability to play steam games and the maker space/hacker community has been having a field day with this. ]