Meanwhile, we're fortunate if a first party Nintendo game sees any sort of price drop in its first year after release.
Price drops are ultimately controlled by the publisher. You do know that based on a landmark Supreme Court case (can't recall the case off the top of my head - but it was decided a while back), retailers are actually prohibited from selling items below a certain price unless consented to by the (in this case) the publisher. Nintendo games *rarely* go down because Nintendo won't allow it.
When games drop the way they do, it's not merely because a retailer wants to get *rid* of it. It's because the publisher -- who probably is seeing really bad sell-through data -- needs to move units.
Of course, price drops are not always because a seller sees bad sales data - I would argue Sony's aggressive moves with the PS4 price in past years was based on trying to keep momentum, and to kick Microsoft while their down. Now, on the other hand, its moves are probably based on some fear of Xbox One's slow but steady rises in sales performance - not that Xbox will ever pose much of a real threat to Sony this generation.
Bottomline - the prices are up to the seller. Good games tanking are not a *new* thing, but we seem to be seeing more and more AAA games (e.g., Doom, Titanfall 2, FFXV ... and now even COD) collapsing in price shortly after their debut. It means publishers aren't seeing the sales numbers they need and that could soon mean publishers unwilling to spend the dollars to make AAA, console games.
Sure, there's a lot to unpack in terms of *why* good games fail (marketing, design, timing, etc.), but there is something to be said about how consumers are valuing AAA console games compared to the growing pervasiveness of F2P and <$1 mobile games ... those games monetize their development in a way that IMHO would be very bad for console games.
We've already started to see some of the effects in DLC, patches, micro-transactions, episodic releases, etc. and these aren't all bad things. However, drops like these may mean some fundamental changes will have to happen on the publishing/developers' ends to better monetize their games.
It's a tricky and complex business - and while lots of choice and dropping prices are good for consumers -- well, it also means that as consumers pick certain games, the industry may leave other sorts of games behind (JRPGs ... I'm looking at you).