Perhaps it's just nostalgia. I still own my DS Lite, though.
In 2004, the games I played that had come out ~22 years prior, give or take two years, were already considered retro: Donkey Kong, Pitfall, Pac-Man, Asteroids, etc. And ~21 years prior was the great video came crash of '83.
Suffice to say, we're dinosaurs. I've made my piece with it and spend a considerable amount of time listening to old British dudes break down 30 year old games.
For me it's the fact that I can emulate basically all retro consoles on the n3ds, including imo the best existent way to play VirtualBoy games in actual stereoscopic 3d. That on top of the fact that it's the only way to play 3ds games in the native experience, with 3d, which is impossible on any emulator. Combined with the social features and build quality of the device, and it's unbeatable. Get a USB 3ds charger and it's the perfect travel console. I bring it on every trip and leave it on streetpass mode. Especially for Japan trips, I still to this day pick up new street pass pings, which is so incredibly delightful to find when I get back to the hotel room.
Though I prefer the non xl version, as it's a truly portable console rather than the XL which is huge and heavy in my bag.
You can get that with a headset; there's emulators for the Quest, or you can use Citra in SBS mode with a headset like the Vision Pro or Xreal glasses. But yeah it's more finnicky for sure.
I wanted to be wow-ed at the level of that old cowboy arcade hologram game. :)
I'm sure since it was the newest hardware it was the best.
Sega Time Traveler
Playe it a few times. Never made it very far. Sure was cool to look at though.
But I think the 3D served one really wonderful purpose: it made the small screen feel larger overall. Not large, maybe, but larger than it really was.
Less popular opinion : the ps vita was also one of the greatest despite Sony's horrid support and faith in the product.
The DS Lite can fit in your pocket. Comfortably. Not, like, technically fit, at the cost of making it uncomfortable to walk around. You can keep a DS Lite in your pocket all day, ready to be pulled out the moment you enter the crowded subway, or while in the doctor's office. Situations you didn't necessarily plan for.
The stupid Switch, and especially the even larger Steam Deck, I never actually have with me when I want it. All I have is my stupid iPhone, which is great for many things but doesn't have buttons, and it turns out you kind of need those for games. Developers have been trying, for nearly two decades now, to find ways to avoid buttons, and it even kind of works sometimes, but not really. Not when you want precise control over a character.
No one makes portable consoles anymore. I mean, they're portable in the way that a laptop is portable. They're handheld in the way a vacuum cleaner is handheld. But they're not portable like the DS Lite or GBA SP.
You can buy these little Android things designed for emulators, and I've almost bought them a few times, but I've pretty much already played all the NES games I want to play, and because there are very few new NES games being released, the library doesn't expand.
[1]: https://retrohandhelds.gg/trimui-brick-hammer-review/ (most links are to third-party resellers, so a link to a review is probably safest)
Now, what I would almost certainly buy is a Steam Deck in that size. It doesn't need to be as powerful as a Steam Deck (impossible, of course), just enough to play 2D indie games.
Many people talk about the Steam Deck, when in reality it isn't that much of a hit in units sold compared with any portable games console from Nintendo, SEGA, Sony.
I haven't bought a Steam Deck because I think it's (1) too big (see my sibling comment on console size—to be fair I own a Switch 1 and 2, but the Steam Deck is even bulkier) and (2) too fiddly, this is the thing I've never liked about PC gaming.