what is the best snes emulator and is there a gba emulator for r4

can someone tell me the best snes emulator and if theres a gba emulator for r4 theres one for ds iplayer

The only reason there's a GBA emulator for the iPlayer is because the iPlayer has it's own built in cpu. So it's impossible for the R4 or any other normal flashcart. The Supercard DSTwo can, because it has very similar hardware to the iPlayer, but it's not out yet.
As for SNES emulators, if you mean for the DS then SnemulDS is the best, although compatibility isn't too good. There are more for you to try here though.
If you mean SNES emulators for the PC then I personally like ZSNES.

Replying to #2

A lot of the links i have tried on his list are dead now.
Would love to see an update on this.

Replying to #3

Oh, sorry, I didn't know. But it's useful as a list of emulators, and a google search will find their websites pretty quickly.