He means system specs and not species (like homosapiens etc ).
In my opinion ePSXe 1.4.0 with Null2's spu and Pete's OpenGL GPU are best, however some things are better for some peoples systems than others, for example the glide gpu's are much better for systems with 3dfx based gfx cards etc.
VGS - perfect (although in software)
Full 3D :
Bleem! - Perfect, the best in 3d (but still have minor sound problems)
ePSXe - Perfect, but you need a bit of powerful system than what you need with bleem!