Completely unique and very difficult to experience with alternative hardware nowadays (compared to the PSP which can be played on nearly everything). The games library is incredibly unique because small budget games still had a big chance to succeed.
Every PSP I own must have the following games ready to go at any time:
-Lumines
-Rock Band Unplugged
-Patapon 2
-WipEout Pulse
-Final Fantasy: Crystal Defenders (gorgeous small tower defense game, but with enough strategy behind it for hours of play)
I acquired my 3DS before the first price drop and unfortunately I never really appreciated it while I had it. It was the first place I played Ocarina of Time, which was a really fantastic experience that I was probably too young to really appreciate at the time. I never got around to playing A Link Between Worlds unfortunately. Beyond that my other favourite was Mario Kart 7. There are a lot of games that I now wish I had picked up but didn’t get a chance to.
The 3DS is also really interesting as it’s currently the last Nintendo handheld that can fit in a pocket. That era of portable consoles has largely passed out of favour (this is why I’ve started collecting PSP Go consoles). A lot of the best 3DS games have been somewhat overshadowed by the Switch now. I feel like its game library may be remembered similarly to the Game Boy Advance, more iterating on older franchises rather than having its own hugely impressive identity.