GP32 was the first.
I had a great time playing Genesis games on the go.
It was good for NES and Genesis, which was exciting at the time.
The PSP was a really good successor. I had the original at one point and a Go at another point.
Didn’t have any trouble with NES, Genesis, PC Engine, or PS1 games, and SNES was often playable though rarely perfect.
Worst for a strange reason was probably the Xperia Play.
At the time the Play was my game system and my phone. I liked it, but I’d run down the battery playing games, so my phone would always be either dead or low battery. It definitely turned me away from the idea of ever using my phone as an emulator system. I don’t like having to be mindful of charging my phone. This wouldn’t be an issue for someone who charges their phone more regularly.