Right, the supposed scarcity of sealed games differentiates it from tulip bulbs, but the big point is that there's always the potential for dramatic revaluations of sealed games by the market. Buyers slugging out protracted bidding wars on eBay are one example of why this could happen.

It all comes down to common sense, and common sense says to diversify your investments. You can put some money aside in sealed titles (if I were to do it, I'd forget about classic stuff unless I could find it at thrift store / clueless flea vendor prices, and focus on getting games from the last decade that had fallen dramatically in price and which I assumed could go higher...unfortunately for me, it's anybody's guess whether people will give much of a damn about stuff like PS2 Shinobi or Otogi II; sealed games collecting seems to benefit people who cater to the great unwashed of gaming, but I'm starting to make value judgements...)

As an unrelated aside, I will say that I would lose much less sleep over money in a CD than I would over games sitting in a house where they can be destroyed, quickly or slowly, by any number of factors. Money in your bank account doesn't suddenly turn out to be counterfeit, or stuffed with twinkies, and money is always convertible. I have some rare stuff and I would say "good luck" to my earlier self asking myself to believe I'd be able to flip it easily...money doesn't pose that problem.