I'm thinking of buying an extra copy of Omega Ruby and Alpha Sapphire in case the market value increases over time like Soul Silver and Heart Gold does. But I'm also wondering what other Nintendo game this generation can do this. I think Super Mario 3D World and Donkey Kong Country: Tropical Freeze will sell for a lot in mint condition when the next generation is at its peak.

And here's soul silver's price in Amazon. Keep in mind this game is only three-four years old.

http://www.amazon.com/gp/aw/d/B0038MTE7C/ref=mp_s_a_1_1?qid=1415817972&sr=8-1&pi=SX200_QL40

Super Mario 3D World might not sell for over what it's new price is now because Nintendo will always ship that game. However, DK:TF might be a good bet because it's already slowing down majorly and Nintendo will probably forget about it next Summer altogether. Xenoblade Chronicles X is, of course, another good bet if it sells badly.

And no, I don't sell my games. I'm what you call a Junior Hoarder (for games only, though.)

There is a collectibles market for new/mint/inbox video games for sure. There are some people (myself being one of them) that would prefer the pristine box to display over just the cartridge/cd to play. I don't sell em, but I do buy em. :)

It depends on the game. Video games definitely aren't the market you want to buy into if you're trying to make a profit though. Not many games increase in price and you can't really guarantee what games will be expensive over time.

I'm sure no one expected Dokapon Kingdom for the Wii to get as expensive as it did. The PS2 version was cheap all the way until a couple years ago and now it's also kind of expensive, probably thanks to the Wii version. The game looks stupid based on the cover but it's an excellent RPG party game.

Nope.

Generally its those 1st party Nintendo games that always skyrocket in value. So always go for them.
Alternatively those niche but very popular games also skyrocket too (ie: Xenoblade).
Lastly, if it comes in a special edition, then a price increase is just a matter of months.