Question, how difficult or how easy is it for companies to actually do this?
Nintendo for example, is it easier for them to do a whatever classic with 1st party games only?
If so, does that mean that a PSX classic, realistically, in theory would only include first party games because getting the license to second party or third party games would involve more hoops to jump through?
Here's what I'm getting at, lets assume that a Sega Saturn classic wouldn't sell, besides that reason, would it be difficult for Sega "licensing wise" to do something like that?
There are two hoops: rights and price.
Rights is the third party agreeing to their game being in the collection, and price is how much they get (either flat fee or more likely £/% per sale).
Some of them can be further complicated by more rights issues (capcom disney games need disney's agreement as well for instance, and disney will need to be paid, so licensed third part games would be the most expensive to add to one of these collections).
Nintendo obviously don't pay anything for their own first party games.
Sony is in the worst postion as so many of their biggest games are third party, and this is especially true in the PSX gen. It would be absurdly difficult for them to put out a good collection at anywhere near the price nintendo has.
Conversely, it wouldn't be hard at all for sega as tons of the best saturn games were made by sega - they would be in the same position as Nintendo are where they pile on a load of first party classics and then pick and choose from the best of the third parties. Emulation may be an issue though, as the Saturn was complex - you'd need a pretty good SoC to do them justice.