Hard to say. Digital distribution started becoming popular in the early 2000s, and I'd wager there are a number of PS2 games which would be more valuable now if not for repeated remakes and being listed on Steam, but that's largely speculative.
Some effect, sure (indeed prices of Final Fantasy vs various remakes and respins are a fun one here) but despite far superior versions on various consoles since the N64 Rare games are still quite high. Resident Evil might make another interesting test case. Of course Nintendo are probably the exception here (keep finding myself linking
https://towardsdatascience.com/predicting-hit-video-games-with-ml-1341bd9b86b0 but it does show interesting things).
I would guess it is some function of rarity in general, desirability on that console (most of the new to the PS1 final fantasy games had near simultaneous PC releases of reasonable quality), desirability of that console (give or take the neogeo and similar such things -- I doubt the wonderswan is going to do much here but did have several notable versions of games from the same era), quality of any remakes (see final fantasy IOS remakes which somehow spread to the PC, the silent hill collection debacle), how official something is (I am still shocked at the extent of love people have for the mini retro consoles as with the exception of the PS1 everything has been trivial for years and the PS1 was not so bad either) and a few things like that.
Wait so, since digital copies/licenses or however you want to call it don't deteriorate with time, how do you assess their value? People would just sell it at slightly lower than the selling price to "beat" steam, and others would sell lower to compete. Steam would then have a extremely massive drop in sales, this so called used market is a brand new condition market. Who in their right mind thinks this is a good idea? Yes it would be nice if as customers if we're treated as royalty, but this is going too far. This could very well potentially drive Steam out of business, what then? Where's your licenses now?
Similar to what ThoD said, you do agree to Steam's ToS when you use their service, there is no violation by them here. If you don't like it, buy from somewhere else, or make your own key reselling store.
Please think a little before going all guns blazing saying I want everything beneficial to me and everyone else has to adjust, that's now how this works.
Again there are rights you can't forgo in a contract (see unenforceable terms) so this could be one of them, indeed the court seems to think it is.
Do physical games deteriorate quickly enough in sufficient volume to not cause the same scenario? I am sure there are some that buy games in cash, slip on (and shred) the receipt on the way to pop it into the console and in doing so snap the disc/cart in half as they land on it but the majority of things don't and as such you could find just about any 2 year old game in mint condition. If that represents the vast majority of income for most (the percentage of games that go on to dominate multiplayer spaces, or indeed become a sport, become test case games or become elder scrolls/GTA/similar in their ubiquity is minimal -- probably comparable to those tech companies that not only get venture funding, not only succeed but don't get bought and then become one of those players that buys other companies) and has not happened yet/did not happen during the decades since software was divorced from hardware then is it likely to change much here? Ditto most physical goods while there is ebay and amazon around?
If people presumably had to buy the thing in the first place then the incentive (barring need for a quick sale) is not to lose the money. It would mean Steam has some competition but that does not seem like a bad thing. Such competition could also happen if one of the alternatives actually manages to take off.
Is this customers being treated like royalty or allowed the rights every peasant is granted?
As for steam going out of business (oh what a glorious day that might be) then technically the licenses are still extant. But yeah it is a problem associated with DRM encumbered goods -- wouldn't be the first and won't be the last. It is generally considered part of the bargain. If Valve truly are the magnanimous gods of the gaming world that some paint them as then they could strip the DRM from it (or whatever they legally can strip... I don't know what goes here as far as agreements with other companies) as a parting gift, and I imagine some company would rush in to take over the Steam database.
Edit
It would be nice to be able to sell games from my Steam library, but I also think that this is the wrong way to go about the matter. I' m not sure the court has thought this one through carefully. I also find the term of 1 month implementation kind of stupid. We would probably get some shoddy implementation that would cause all kinds of problems. At least give them a year or two to make a good system.
They already have a gift function which allows you to send your friends your "unused" games. Compliance by virtue of actually deleting a bit of code that says "if played then don't allow gifting" (though in reality probably if location = France then allow, they presumably already have fairly decent geolocation services baked into it) and telling people sell it on third party services could easily be achieved in a few hours.