I think a lot of gamers are hitting the age of their 30s and they want those classics they grew up with.
Also, on eBay, you can find that classic game easily, but you have to pay a premium for finding it so easily. Want it cheap? Then hit up the garage sales.
This is exactly it. For those in your late 20s-early 40s, remember how baseball cards were huge when you were a kid, and there was a huge market for them? You know why that was? Because that's what your dad collected when he was a kid, and he was trying to recapture a part of his youth. Demand up, supply stays the same, price goes up. There were obviously some rare cards out there, but the market peaked when people were buying entire seasons of that current year in order to get a rookie card of that year's top player(s), because it would be "a good investment". Most of that stuff isn't worth much now, because that generation got over it.
Same thing will happen with our generation. The big differences in video games compared to cards are:
1. Games/systems cost a ton more to buy as compared to pictures of people on cardboard. It was so easy for a mom to throw out some "silly cards" after their kid went off to school, not to mention they are much smaller (again, easier to toss).
2. Mass production. Most of the games for the mainstream systems were made in the hundreds of thousands, if not millions (or tens of millions sometimes). I don't have any stats to back it up, but I would be willing to bet that there were a LOT more copies of Earthbound made than 1914 Babe Ruth rookie cards.
We're definitely in a bubble, and it will collapse as the people in our generation with only a passing interest/nostalgia move on to other things. If we learned anything from housing in 2008, what happens when a bubble pops? Good news for you collectors out there.