(4) I notice Sony games seem to be conspicuously absent from your list. Not sure if it's because you were trying to be practical and take shots at MS games because they're more likely to be ported.
Nothing conspicuous about it at all. Most of the games I mentioned were multi-plat or 3rd party, I just personally played them on 360 because the PS3 was an incredibly poor choice in its early life. The Wii and portables are too architecturally and tech-base dissimilar such that it'd be pretty much impossible to do direct ports rather than remaking the games. Also the Wii, PSP, and DS, and the PS2 and everything before the PS2 can be emulated so I don't really see much urgency in securing PC ports or versions. So really the only thing I left out was PS3 exclusives. Sony isn't going to port any of their games (SOE already ports all of them, SCE won't port any of them). The PS3 had relatively few good third party exclusives, at least to my taste, so I didn't mention them.
But since you ask, I'd like to see:
Retail
3D Dot Game Heroes -- this would definitely get some traction on PC. User-customized content meets a Zelda game in the vein of the NES Zelda games. Developer is still solvent. Published by From in Japan, Atlus in NA.
Final Fantasy XIII (not exclusive, but substantially better on PS3 than 360) -- I guess I'd like to see it ported, but I didn't like the game.
I've written about it many times, including here.
Kingdom Hearts HD Remix -- Yeah, sure, I'd like to see Kingdom Hearts on PC. Ultimately though as a port of PS2 game it can basically be played in a PS2 emulator (and the original game is dirt cheap and I already own it) so I don't really feel it's urgent.
Metal Gear Solid 4 -- I dunno, I don't really like Metal Gear Solid 4 from the hour or so I played of it. And it never got ported to 360. Probably more feasible to aim for a port of MGS
5 instead. Konami has published games on PC, but Rising is a better fit and Platinum seem to be technically proficient devs in a way that Kojima's mainline team maybe aren't so much.
Ninokuni -- I haven't started this yet. I can't imagine it'd be a smash hit on PC. Namco has published games on PC before, but Level5 has never developed anything for PC have they?
Valkyria Chronicles -- Again, I don't expect it'd be a big hit. It's a neat game. Sega never even patched in trophies though, so I wouldn't expect they're eager to dig it up, and both future sequels were portable... The team that developed it also doesn't exist anymore, do they?
PSN
Okabu -- Although Sony technically published this, I don't think they own it. Maybe they do. If they do scratch it off. It's the company that made Rolando, and it's a really cute but kind of shallow kind of puzzle adventure exploration type game. Hard to describe or compare it to anything. It's really cute. I don't think it did well for HandCircus, who are apparently working on a mobile title right now. I don't expect it'd do super well on PC because of so much competition from cute independent games, might be a lot of noise.
Tales from Space: About A Blob -- The sequel, Mutant Blobs Attack, got a Steam release and seemed to do OK. I liked this. Maybe Sony owns this IP as I know they provided some funding for it.
The Unfinished Swan -- I think Sony technically owns this because the developer had to call in Sony Santa Monica for development assistance, but this was a great little game. It's a first person adventure, like a Portal or something. The main mechanic changes throughout the game, but the first segment involves the whole world being white and you being able to shoot blobs of black paint that splatter realistically. I won't spoil future segments, but the mechanics work the whole game through. It's a really sweet little story that reminded me, intentionally I think, of The Little Prince. I'm certain this would get an audience on PC, but again it's not clear they could port the game if they wanted to.
That's about it that I can think of, in part because I did most of my gaming on the 360 and all of my multiplatform gaming except FF13 on the 360 and enjoyed the 360
vastly more than the PS3 as a platform.