The value of anything is always a direct relationship between availability and desirability (aka: supply and demand).
The reason games drop in value shortly after release is because shortly after release their desirability drops (people have completed the game/moved on to other games) and the availability increases (people are selling their copies used while there might still be new copies for sale too)
Given a long enough timeline the value of any product will INCREASE.
Eventually the game will no longer be produced, and the availability of good condition/new sealed examples will decrease, this will help drive the value back UP.
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Collector's Edition releases will almost always hold their value better than standard editions because fewer of them were produced and production stops sooner (hence the supply is shorter).
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Some games, some editions will be worth more than others and this is controlled by availability and desirability.
if you want to know if a game will increase in value or decrease in value ask yourself this
-will people still be talking about and wanting to play THIS specific game 20-30 years from now?
-will the popularity of the game increase after release or decrease after release?
-was the game hyped up a lot before release?
the answers to those 3 questions will pretty much determine the value of the game down the road.
lets look at Bioshock 2:
- in 20-30 years I doubt anyone will give a sh*t... they might care about Bioshock 1 but people have already forgotten about BS2
- the popularity took a nose dive after release when people realized it paled in comparison to the first game
- the game was hyped up a ton before release
now lets look at Dead Space:
- in 20-30 years I think people will still be talking about the first Dead Space, it was a unique game and spawned a now popular franchise
- the popularity has increased after release when people realized it was good. Also the second game was good which brought new interest and fans to the first game.
- the game was barely hyped before release which meant sales expectations were low as were initial production numbers were low.
not even looking the CE releases the regular first edition releases
Bioshock 2: gets about $16:
http://www.ebay.com/itm/Bioshock-2-X...item19ca9936ee
Dead Space 1: gets about $45:
http://www.ebay.com/itm/XBOX-360-Dea...item4cfb509a54