I'm sure some of my games (maybe all of them) have lost "value". But then again, I don't think I have any item here that is worth more than I paid - TV's, cars, furniture - so why should I expect my games to be an investment?
As mentioned earlier in this thread, the games are for fun, and most on mine have paid for themselves in fun over the years, so I'm not concerned, and lower prices mean more access to more games - I'll take that as a good trade off for decreases in the value of other games I own.
Sure, it's nice when things are worth more than I paid, but it's a cycle with "collectables" and right now demand is down.
Take a look around the world at real estate prices - nothing is immune from cycles (and watch here in Oz in 2013, we have escaped to a large extent to date, but economic forces are ready to explode.....)