I wouldn't do anything in terms of "rarity". How many times have people speculated games value to rise and been right? If you're into games for an investment, you are in the wrong hobby. 99% of them drop to a fraction of their retail cost after a few years, and only a handful of those rise.
For a little experiment, I would definitely stick ICO and/or Wander and the Collossus in my capsule, just to see if they have any type of impact on gaming in general. Both feature something that far too many games don't. Light story, heavy gameplay, and (this one is very key) almost no music. 5 years ago I would've done the same for Shenmue, but based on the first 5 years after it's been out, it has had little or no impact on market, unfortuantely.