There's no other place to play Demon's Souls, so PS3 for that one. Then you can move on to the PC for DS1 and 2 and appreciate how much better it runs.

As stated Demons Souls is PS3 only , if you are only on to Dark Souls and can wait for the PC release of Dark Souls 2 then the PC is the best bet

This. But I would remind/inform him that GFWL will be shut down very soon, so if the online aspect is important to him or he doesn't want to deal with cracks he should get the PS3 version. At least wait until GFWL is terminated to see if they patch it out. I highly doubt they will adapt the multiplayer to another client (Steam), but maybe we will be able to authenticate our copies without having to use cracks. Demon's Souls should keep you busy until then.

You really should play the PC version of Dark Souls 1 and later 2 with some added mods.

@ezekiel: Ah yes, GFWL. We do know that DS1 will move on to Steamworks when GFWL shuts down and DS2 will start out of the gate with it. Demon's Souls will likely take up his time until it dies sometime in July.

DS1 on PC with mods runs great. So Id play that there.

Like I said in my edit, I highly doubt they will adapt the online to Steamworks. That seems pretty complicated. They've said they're looking for solutions, but I'm not even very hopeful that they will remove the GFWL authentication and interface/client, since they never patched in any of the missing features people expected, like HD and stereo.

PS3 only for Demon souls and Dark souls 1 & 2 on PC. By the time you finish Demon souls and Dark souls Dark souls 2 will be out on PC!

@ezekiel: Didn't see your edit. That is unfortunate news, I thought I had heard that it would be absorbed by steam, but I suppose not.

May as well stick with PS3 for the better portion of the series OP.

Well PS3 is the only place to play Demon's Souls so either PS3 only or Demon's Souls on PS3 and then Dark Souls 1 & 2 on PC.