It's understandable. NES and SNES were much older, more established systems when it comes to the second-hand market. GameCube was a largely overlooked system that was in the right place to get a nostalgic upswing, and also had far less actual physical stock compared to systems like the NES and SNES. (On account of having never moved as many units when it was actually being sold) It's the GameCube's time to shine when it comes to second-hand sales. It also doesn't hurt that we are finally getting some decent third-party video adapter options for the GameCube, allowing it to look a bit better on modern flat-panel screens.
The PS1 and PS2 aren't going to have nearly as much of a bump, on account of them having an enormous amount of units. Also, the second-hand game market for those systems is extremely well established, and most of the super-expensive games for them are already quite expensive. They might see a slight bump when Sony's streaming system provides some of those older games with extra exposure.
The later console generations are going to be odd for second-hand collecting. The 360 and younger featured near-parity in overall unit capacity, as well as some of the longest console cycles in history. This means tons of actual stock, so practically non-existent scarcity, and very long generations during which people could start collecting. It was also peak time for second-hand stores like GameStop, so actual games were plentiful and cheap, with lots of shopping options during their actual lifespans. Games and systems from those generations are going to take way longer to rise in price on the second hand market. Savvy collectors simply went out and got the games they wanted when they were still on store shelves.
