Replying to #1
Just by the mention of certain games, it seems that you are going completely legit. Also, I think 160 GB will do for what you need to do. If you ever plan on going bigger, then don't concern yourself with the HDD size because you will be upgrading it. Just something to think about. No need to get a big HDD if you're going to put an even bigger one in there.
Not many good RPGs out there for the PS3...at least JRPGs...
There's Dragon Age I & II, Mass Effect 2, and Fallout 3 for WRPGs.
As much as I dislike Final Fantasy XIII, it is by far the highest quality JRPG we have on the console, unless you actually enjoy NIS-developed crap. Nippon Ichi Software is the sole reason I give FFXIII such high praise. I didn't like the battle system until I played anything published by NIS. Auto-battle is great, as long as I don't have to manually move my characters around, or have to analyze really over-complicated battle mechanics. I'll take Auto-Battle any day. Linearity was kinda boring, but it's better than not knowing where the hell to go. Voice-acting is Emmy Award winning compared to the corny ass dialogue that NIS presents.
There's also Resonance of Fate, but even now I still don't get the battle mechanics...
Folklore is more action-RPG, and Eternal Sonata I haven't played.
Valkyria Chronicles is a strategy-RPG, and is really good.
Ar Tonelico Qoga, Atelier Rorona or Totori, Cross Edge, and Trinity Universe (even Disgaea 3 & 4) are all published by NIS, and going from FFXIII to any of these titles just shows a lack of effort on their part.
There's also Rune Factory: Tides of Destiny, but I haven't played it on the PS3 yet.
Also, there's Borderlands but that's an FPS game heavily based on MMORPG concepts. Get the GOTY edition or don't bother playing. It needs the DLC packages to be enjoyable.
And obviously, you're going to have to at least rent the PS3 exclusives like the Uncharted series, God of War series, Infamous 1 & 2, and Tomb Raider series.
You'll also need
A racing game, so GT5 will do. I didn't really like the arcade-ish racers like NFS Hot Pursuit or Test Drive Unlimited 2.
Sandbox games:
GTA IV, The Lost and Damned, The Ballad of Gay Tony
Red Dead Redemption & Undead Nightmare
Saints Row 2 (haven't played 3)
L.A. Noire
I think I covered most of what the PS3 has to offer, as far as legit means.