DS has a little advantage over the PSP, 3DS would be a close third and Vita is dead last, it's so bad that I put mine back in the box months ago and then two towers of games from the other three on top of it, not going to use it anymore and I doubt I'd be able to sell it.

3DS definitely, I love the DS family

I am torn betwenn Gameboy and DS, but Ill say DS simply because I think i enjoyed it a bit more.

3DS in first, DS in second, PSP third.

My all time favorite is PSP, had so many great games.

former PSP & current Vita owner here, Vita ftw

3DS by far. Haven't played my Vita in years.
DS would be second.

The PSP beasts everything

Out of the ones I've owned (GBA, PSP and 3DS) I'd definitely go with the 3DS. I've gotten hundreds of hours of enjoyment out of New Leaf alone, and it's also the platform that I first played Pokemon on, as well as some of my favorite Zelda games (Majora's Mask and ALBW namely).

GBA SP

Awesome battery life, backlight, so not a problem to play outside in the sun, awesome games. Also, its compacity was the definition of portable, in portable console. It was a small SNES actually. It had fuckton of cool games, Fire Emblem, Mario Kart, FZero, Metroid, Advance Wars, Pokemon ...

I loved the GB SP. Never had a GBA Micro though.