Geist was a game that would make a great sequel, especially in today's gaming world. Ghostly powers, haunting things and scaring them guards, and solving puzzles, all while being a ghost? Yes please! Just don't make the final boss so obnoxious to fight...
I'd say Sly Cooper, but we've got that coming, how about a Sly Cooper made by Sucker Punch? Seriously, I love the series and I'll buy 4, but I'm scared, since it was the writing and the strong focus on a blend of comic styled story telling filled with realism and drama. Like Batman if he was really a big bat, and robin was a bird, or whatnot. I mean, Sly 2's mid-section with the Contessa? Wow, I couldn't believe it, and the way the characters grew in game...oh glorious. Even Sly 3, not as good as 2, still started the game in a great way...I'll stop here or I'll have a novel on how much I love this franchise
I wish when a company made a series, they didn't have to give it up, because you get the Duke Nukem effect, a team that wants to keep the series going, but at the same time, makes the game a bit worse when they suck the game's virtual wingy-wang and not force innovation the way the original team would...