Don't count this toward the Dojo's number because I already posted it on NeoGAF but I'd donate $500. But it would have to be a sequel and there would have to be solid evidence the game would be made and that it wasn't just pre-planning. And the game would have to conclude the story. I don't want to experience the frustration of the last 12 years again. Support-level bonuses would be cool, but a game is what I'm after.
EDIT: If we're just talking about a vague "we want to make Shenmue but need money" campaign that could eventually sink, I would only donate $150. I'd only donate $50 for HD remakes.