You're not actually looking to beat Ghosts and Goblins are you? Because as much as I'm a bit of a masochist sometimes, that's one thing I'll never be able to bring myself to do.

Anyway, I'll make a list of the games I'd play first, and a list of games you should sprinkle in here and there because you can either chip away at them gradually, or because going at them full bore might lead to suicide. Personally, I'd focus on games I hadn't played or wanted to finish first and foremost.

Silent Hill 2 - no brainer.
GTA Vice City - my favourite GTA and the only one besides 3 I could ever bring myself to beat, let alone play more than once.
FFIV The After Years - just because I'd like to play it myself to be honest.
Shin Megami Tensei: Digital Devil Saga Part 1 - I'd love to give this and the second game a go. I'm jealous that you got it cheap so I say play it.
Metal Gear Portable OPS - How could I not recommend playing through a Metal Gear? I need to pick it up myself.

As for the games to sprinkle in here and there:
Super Mario Galaxy - I wouldn't really recommend it to be honest because I didn't like it at all, but if you're intent on beating it you can always grab a few stars here and there without too much effort.
Ghosts and Goblins - I'd have a hard time playing through too much of this at a time without throwing a NES out the window, but in short bursts this kind of game is perfect.
Katamari Damacy - Easy to play in short bursts from what little I've played myself.
Onimusha 1 & 2 - I liked the first one back in the day, though I'm sure it hasn't aged well. Still, they're short games that you could get through in smaller chunks.