can someone please enlighten me on the issues for yoshis island, mario allstars and mario RPG?
is it on PSP/PSV only?
This isn't really a complete question, or the first portion of it would be, but the "is it on psp/psv only" part makes it appear that you are asking something else.
If your question is
"What is hard about emulation of Yoshi's Island"
It uses a very late version of the Super FX chip which is rather tough for the SNES to emulate since not only is it running the SNES hardware but also the equivalent of a graphics card plugged into the system along with this game.
If however you are asking
"is this issue with emulation of these titles specific to the psp/Vita"
Well, no it isn't, but PC's now will have no trouble running an emulator at full speed with these games, but any hardware with just just on the edge of being able to run the SNES itself will be severally hampered by the Super FX chip games.
I will add here btw, that Yoshi's and RPG both use the Chip in question, there is little to no issues running Super Mario All Stars or Super Mario All Stars+World Rom on the Vita as that doesn't use any extra hardware chip.
https://en.wikipedia.org/wiki/Super_FX
The same issue happens with Doom on the SNES, again though, that game also has a GBA version which runs as smooth as butter in GPSP for Adrenaline.
But yeah as you can see from Wiki the co-Processor runs at 28mhz, compare that to the 2.7mhz in the base model of the SNES and you can understand why the games which feature this chip really strain emulation of the platform, when you consider that the PSone runs at 33mhz this chip alone is coming close to that in terms of speed and power (but in a far more basic way and without memory)