Just to really drive in what the others are saying..... no offense at all, but in general it is a waste of time to put console games on an arcade cabinet both due to control issues AND due to pacing and gameplay differences.
There are a few strange exceptions though and this list applies to all consoles, not just the psx:
1. Arcade titles that aren't emulated yet.
The psx in particular has the best Time Gal and Ninja Hayate ports available (laserdisc games), going even so far as to use the original roms. This list used to be quite long on the psx, but now that cps2 emulation is long mastered and the simple 3d games are emulated in mame and elsewhere this isn't the case anymore.
2. Sequels to popular arcade games that never made it back to the arcade.
Splatterhouse 2 & 3 come to mind on the genesis. There are a select few games out there that were originally designed to be arcade titles but for whatever reason only got released on consoles. I can't think of any on the psx though.
3. Lightgun games.
Of course this only applies if you have a lightgun of some sort. Gun games are in short supply, even in mame and many of the best ones just aren't emulated yet. The psx has a pretty beefy selection of gun games taken directly from the arcade that aren't even close to being emulated yet. I have these, and only these psx games on my own mame cab.
As to how you set it up.....
I typically treat psx titles like I would a pc game, simply because there are so few I would actually want on my cab and psx emulators are tricky. I might have to load a save state to boot directly into the title screen for example. (I do this for the laserdisc games perviously mentioned)
Then again take this with a grain of salt as apparently I'm a "Nintendo Fanboy" and I "Hate Sony". Of course it is true that nostalgia doesn't fall into the equation when I'm making my psx selections.... back then I was playing the infinately superior n64.
