I'd actually include the Switch as well. For a mobile device launching in early 2017, it was a very capable machine. Games like FAST FMX, Mario Odyssey, Breath of the Wild, and Mario + Rabbids Kingdom Battle were among the best looking mobile games on the market when they released.

Gamecube didn't have top visuals, the Xbox did.  But the GC was more powerful than ps2.  

Gamecube wasn't the most powerful console of the generation by raw muscle, but games like Rogue Squadron II, Metroid Prime, and RE4 had some of the top visuals on consoles at the time of their release.

They might (and probably should) make a cheaper version of the Switch that doesn't have a screen and battery, etc.... but they aren't going to have two incompatible systems with a different set of games.

It did some things better. Like DC did some things better than PS2 even if could not match its PPS. Gamecube was pretty powerful as consoles went back then. I'd have to go find it but I think Rogue Squadron III was one of the highest polygonal pushes that Gen had and the highest for Gamecube.

Xbox was way more powerful, but RE4 looked better then anything. Even on ps2 my jaw hit the floor and i owned a xbox and thinking to myself this looks better then anything on xbox. I can't imagine how good the GC version looked. xbox really had so much wasted potential a Resident evil 4 port would have been amazing. 

GC version was odd.  It was wide-screen but cut to 4:3 so it was a much smaller screen.  Or something like that.  I can't recall the exact details but the ps2 version was better just because it was had a better aspect ratio.  

Edit

Rogue Squadron was impressive.  Apparently factor five used a bunch of custom techniques.  Even today emulation of Rogue Squadron runs like crap. 

Personally I was most impressed with MGS3 and FF12.  Both of those games were well optimized. 

The GC was "letterboxed" (black bars at the top and bottom) while the PS2 version was full widescreen, but the PS2 version had a number of downgrades to get the game running on its less powerful hardware; textures, polygon counts, lighting, and effects were all downgraded compared to Gamecube.

Yep, I'm aware.  But letterbox made the GC FoV super small.  I preferred the ps2 version because it was much larger.  My vote is for the ps2 version.  

At the time I had a 16x9 TV.  The gamecube version, including black bars, was cut to 4:3, but displayed 16x9 within the 4:3 cut.  Meaning the actual game took up like half the screen.  

To this day it is one of the oddest developer decisions I've seen.

Edit

Not that it matters because RE4 remakes blows the original out of the water across the board (e.g. graphics, gameplay, etc.).

rallisport challenge 1 and 2, ninja gaiden black, chronicles of riddick, and splinter cell were pretty great on xbox graphically but i don't why resident evil 4 on ps2 had me so impressed that it didn't make sense to me at the time cause i was told that xbox was way more powerful and it was but it just shows how good the developers were and the damn game was suppose to be a xbox exclusive but the meeting went so bad with capcom that they went to nintendo lol.