The only reason there isn't a Demon's Souls 2 is because Sony owns the IP and they wanted to go multiplatform.
Armoured Core 5 tells me From isn't exactly adverse to the idea of sequels.
I am a huge fan of NMH and would certainly like to have Lollipop Chainsaw on PC.
The reasons why I feel Vanquish in particular would be a good game to push are the following:
1) It's a game that would appeal to the PC gamer demographic
2) It would benefit from a PC release due to the unstable frame-rate and less precise controls of the console version
3) SEGA are generally open to releasing their games on PC
I don't see why the age of the game is a big deal. If SEGA's Dreamcast ports can be profitable, I don't see why this can't.
After the Double Fine Kickstarter success I thought no other game would ever be able to raise that kind of money. Then Wasteland came along.
No one has really tried to push a PC port the same way Dark Souls was pushed. No other game petition has had its own dedicated thread on NeoGAF. This actually surprises me as I thought the Dark Souls port was going to spawn several similar campaigns.
Well, there was the operation Rainfall thing before, but I think the kickstarter campaigns kind of took over the niche of fans trying to organize and push for something.
I'll agree with Tuco that 40K is a ton of signatures though. To get those kind of numbers you really need to get someone like Total Biscuit or Notch to shill pretty hard for you. On the plus side if you manage to actually get those kind of numbers they more or less have no choice but to at least give an official response.