The Ultimate Sith edition of Star Wars: TFU has also retained it's value so far. One way to see if things from a few years still sell(besides looking online) is to check out your local Game Stop. I know it's not exactly the best measurement for this kind of thing but when you see that they are still selling used copies of Metroid Prime Trilogy for $50 or 60 and other used games for high price points, chances are those are still in demand. Rather that demand will last another 5+ years is anyone's guess.

The only games I see retaining their value for the forseeable future are the limited editions of the first Mass Effect and Bioshock. Even used those still command a pretty solid mark up.