Batman or Uncharted. Everyone that plays the Uncharted games says they are excellent so maybe you should play that.

Arkham series. No two ways about it.

Uncharted is fun, but it's pretty basic. Think of it like a big summer blockbuster. Style over substance. Fun but not fulfilling.

Arkham Asylum is pretty great. I loved it even though I wasn't a big Batman fan. It's a sort of Zeldaish adventure game with simple but fun combat and a pretty good story.

Based on the games you're playing now, I'd probably go Uncharted first. It would be a quick (couple of afternoons) game and a good change of pace from the more slow paced games like Zelda and FF7. Haven't played Castlevania or Sleeping Dogs yet.