Checked my (incomplete, since my old PC games on disc or even floppies are not yet included, as well as a couple console games I have to doublecheck if they still work) list at Pricecharting, and the results are:

1. Chibi Robo (GC, Pal): 178€
2. Fire Emblem: Radiant Dawn (Wii, Pal): 71€
3. Monster Hunter Tri (Collector's Edition, Wii, Pal): 68€

And in between all that: The 30th Anniversary Classic Mario Amiibo, which is apparently worth over 111€

On another note, I'm shocked how little worth a Wii nowadays has: 15€ is similar in price to most Wii games. Switch is still my most valuable console apparently, though my GC isn't far behind, and worth more if I include the Gameboy player.

I also have Wacky Races for the NES. I think that one has gone up a bit.

Wii only launched 5 years after GameCube, but there has been more nostalgia in the used video game market for GameCube. GameCube games sold way less than most Wii games relative to the hype and demand for them since the pandemic and even before that. GameCube also had a more core player base and library which means more games core players/customers want to experience again or for the first time.

Also, there are far more Wii consoles out there than GameCube which helps the console itself command a lower price. 

While all that is true, I was still expecting more like 30-40€, not less than lost Wii games I own.

I thought Radiant Dawn was far more valuable. Huh.

And yes, Wiis are super cheap these days. It's a shame the same can't be said about NDS/3DS systems...

It was higher. Also, I think I made an error, thinking that CiB stood for  "Code in Box" instead of "Complete in Box", though that would only increase the value right now to about 77€

Also, this is the Pal version, other versions may be worth more. And a new or graded copy has a much higher worth.

I have 2 copies of that one.  The one I played and a few years later I found a copy for $15 at Walmart that I snatched up.  That one is still factory sealed and in decent shape.

One of my biggest regrets is that I did something similar with the NES Final Fantasy.  I had the copy that I played and had a sealed copy too.  My dumb ass got nostalgic and wanted to look at the big fold up map again (I had worn the one out that came with the copy I played) .... so I opened the box for a look.  Now it is just complete in box.

About 10 years ago I purchased a sealed copy of Hotel Dusk (PAL spanish) for 30 euros on eBay. Cheaper than at launch! I opened it because my intention was to play it like I just got it new from a store.

Now a sealed copy sells for about 180 euros. Go figure xD

Earthbound.

It's so interesting that EarthBound on Wii U and New 3DS/2DS VC + NSO has not kept it in the low 200s or below. 

There have been plenty of legal ways because of that to play it for 12 years now and yet it's over $350 loose right now. 

If EarthBound only continues to grow in popularity plus inflation over decades, it could be over $1,000 loose one day.