So what do we have here of note...
Ports:
San Andreas, Bully, Max Payne, Diablo 1, OpenXcom, GemRB (meaning Baldur's Gate, Icewind Dale, Planescape Torment, ..), Caesar 3, Heroes of Might and Magic 2, Dune Legacy, Crazy Taxi Classic, Shadow Warrior, Quake 1, 2 and 3, Quakespasm, Half-Life (or CS or any datadisc), Return to Castle Wolfenstein, Red Alert, Tiberian Dawn, Another Metroid 2 Remake, AVP Classic 2000, Hexen 2, Jazz Jackrabbit and Tyrian (there are many more but these I consider to be interesting games)
State of emulators:
-Moonlight while technically not an emulator allows your PC to be streamed to Vita over wi-fi meaning you can play anything from your PC on your Vita
-Retroarch newest version allows System Shock 1 to be played just fine, other consoles are fine (let's say you can play almost anything up and including Playstation 1)
-ScummVM discontinued sadly Blade Runner but stuff like Ultima 7, Legend of Kyrandia, IHNMAIMS or Sam and Max work just fine
-N64 emulation is now almost top notch (Ocarina of Time and Majora's Mask fully playable at full speed), sadly Golden Eye works flawlessly MINUS the audio
-Some PSP and PS1 games can be played full-speed and with native resolution, plus you can play FPS from PSP with dual analogs
-Possibly in the future we might get much better Dreamcast emulation - atm only Mr. Driller runs at full speed (but for example Legacy of Kain is kind of playable); as well as DS emulation
Other stuff:
-There are many interesting apps and plugins to enhance the convenience of use (Retroarch launchers, save managers, button swapping, overclocking,...)
-For some strange reason the scene is still growing with more and more projects coming (standalone original ones or ports of games like Cuphead, Portal 1 or Hollow Knight)
I have to say I really like the Vita now - atm it's cheap, has some interesting games (Freedom Wars, Soul Sacrifice Delta, Killzone Mercenary, TearAway...) but most importantly the form factor and emus.
I consider Switch huge and not very portable and ugly, Steam Deck seems so big I might as well bring laptop with me. Vita is solidly built and is just fantastic to use - when the battery is drained you continue right where you stopped after it turns on, it can stay in stand-by mode for couple of weeks.
It is great to play some "smaller" or older games I would not have played otherwise (playing some old-school adventure on big ass monitor is just weird). After over-clocking I enjoyed DEX very much. And it just fits in your hands, well worth it in 2021 imo