With vintage video game collecting becoming an ever increasingly popular hobby, prices seem to fluctuate from day to day. Through rarity, nostalgia, the desire to own something you didn't own when you were younger, or just the sheer desire to own something, people are placing higher and higher values on many different vintage games.
One thing that I've noticed is that sequels seem to be the harder to find, or more highly sought after video games. In many cases, sequels were either better or were released later in the life of any given console, making them harder to find or more desirable. But what happens when the price of the more scarce sequel invades the price of it's more plentiful predecessor?
Two examples I can think of, off the top of my head, are NES Flinstones and Chip n Dale. Without question Flintstones Surprise at Dinosaur Peak is rare, as is Chip n Dale's Rescue Rangers 2, but what I see is an ever increasing price tag on their more common cousins. And I believe the reason for that is highly lead by greedy sellers not wanting to pay attention to which one they have and potentially lose money.
As we're all aware video game resellers usually tend to just gloss over what they have and magically come up with a value from various online resources. To the untrained eye an ebay search with Surprise at Dinosaur Peak could make someone believe their Rescue of Dino and Hoppy seem like a gold mine. Sure, from a collector's point we would check and make sure that's what we have, as where a reseller in a rush to make a quick buck wouldn't be so thorough.
Likewise, even as a collector I sometimes get the labels of Chip N Dale 1 and 2 confused. I know they look different, but the purple Capcom design throws me off sometimes. Again, imagine being a foolish reseller or someone just wanting to make a quick buck off their old NES games. The time it takes to nail down exactly what you own is potentially costing you money. If it looks the same, price it and sell it! That's what most resellers do.
Another reason is that perhaps the seller in question doesn't know this is a sequel, or that there is any other version than what they have, so they mistakenly just take for granted that is the correct price. Again, it seems foolish from a collector's point of view, but then again so does the mysterious pricing of resellers, so it kind of makes sense.
I'm not saying the other games aren't good, or even hard to find, but it seems that when there is a small series of games for a vintage system, the rare one always seems to drive up the price of the other game(s). A series like Mega Man stands on it's own, as it was six games long on the NES. The weight of the series seems to be evenly spread throughout all six games. Although they each have their own price, no single copy of Mega Man is $200 while the others float around $20-40, merely because they bear the same name as the expensive one.