In pal regions it really depends what your looking for
Lose carts of most good titles pretty much the same except for the hyped games wich didn't increase to much with the exception of n64 pretty hyped atm.
Common stuff as in bad games just for full sets even back in the day they were hard to sell so naturally they are cheaper since nobody wants them except for the small market back in the day were apprantly people did buy lose nes carts of for example pinball for 5 - 7$.
Obviously not really known good games or more obsecure titles will usually stay the same value wise.
Certain really rare hyped games that were expensive some years back have retained their value not really increased much in some cases a bit of a decrease. some fluctutaion it goes up and down but never cheap SOTN ps1 LE for example or megaman x3 megaman x2 vampire kiss etc But than were talking about pretty high prices. in those cases allot people cannot afford it or have to save money for quite a long time or ofcourse a wealthy man who has not yet gotten that game for the collection. That being said most rich collectors want the best of the best so they usually wait for excellent pristine condition items to pop up. This is the reason why minty prices can be allot higher than even excellent copies.
In general if your looking for complete in box stuff in very nice shape prices have increased over the years and supply is not really friendly to many wich is the reason why apparently people will buy them at the higher prices, There are not many nice condition complete in box examples for especially many cardboard released games, Allot of games especially if your looking for nice condition examples cannot be bought instantly on ebay anymore one has to wait for a nice copy to pop out.
Lose carts are usually plentyfull except for some very rare non hyped titles so prices are pretty much the same or a decrease for bad stuff. Price gap between complete in box and lose has increased allot over the years.
Sega especially megadrive genesis has increased double maybe tripled in a few years especially for certain sought after games wich are 100+ titles while they were only 40 - 50 at best just some years back. That being said for allot of snes nes especially cib games the same can be said.
In europe for the stuff that most want even the more obsecure stuff in general has increased sometimes by allot. if you less picky and accept lose or missing things, filler materials plenty of non sport stuff that fits that category than prices have been the same as years back or a decrease in price since their is no reason to own games that you do not want to play. More people have seen the light on the other side apparently
While the market of cib expensive stuff is allot smaller than for the affordable stuff, the supply of the excellent condition cib games is even smaller unless everyone decides to sell their stuff than things can chance.
