And you're confusing amazing graphics with photo-realistic art design. The descriptor, amazing, is just that - an opinion. It's just as if saying Wind Waker has fantastic art direction, too.
And yes, there are games on GameCube when played on the appropriate television set (a 480i/p standard CRT) that look just as great as PS4/Xbox One/Wii U games. Rogue Leader, Wind Waker, Resident Evil 4, Soul Calibur II, Star Fox Adventures (ridiculous fur effects), Pikmin, F-Zero GX, and even Beyond Good & Evil.
Art style or photo-realism..or not, appropriate to its original resolution and viewed on its respective display, yes, these GC games look just as good as the games' and their respective screenshots you posted (look, I can opinion, too!)
Sure, amazing graphics is an opinion and I could be wrong about whether or not they look just as good, but this is not an opinion:
There are games that were on the system that could still be mistaken for PS4/XBone games. Just that good.
There is no game on the Gamecube that can be "mistaken" for a retail PS4/Xbone game. None. Regardless of art style vs. technical merit. If you can post a screenshot of a game that could be mistaken for a game on either console, I will completely concede to the multiple points that I disagree with and bow out of the argument. I am 100% confident that that game does not exist.
Oh, and just as a little aside, Journey (A PS3 game!) doesn't have photo-realistic graphics and looks x1000 times better than Wind Waker.