Ehh. It was and it wasn't. The Xbox GPU was still more friendly and equipped for developers to use than the Wii's was. Even if the Wii beats out the Xbox in pure processing power, the fucking TEV held it back from achieving easy bump mapping and other goodies.
As much as you're right, bump mapping on GC/Wii wasn't exactly rocket science, it's not as if it wasn't supported by hardware (I'm looking at PS2)
I mean Bump mapping (and EMBM) were pretty much standard on DirectX 6 that existed before programable shaders.
Problem wasn't difficulty in achieving bump mapping, surely. (in fact in that regard compared to Xbox Wii was a motherfucking powerhouse)
They're essentially different systems though, so ones strengths are often the others weaknesses; Xbox big advantage would be the fact it had a PC GPU on it, designed for resolutions higher than 640x480 (I mean some of us were playing Quake 3 Arena in 1024x768 in 1999) thus could actually go past 480p "easily" if hampering the graphics throughput was an option (or if it was just running a PS2 game). That wasn't the case with the gamecube or the wii. It also did AA more often (probably related to the fact that the GC/Wii framebuffer wasn't big enough for it requiring some tiling and unpleasant gymnastic whereas in Xbox it was taking RAM from the main memory pool but was "more" doable; specially for 2001 standards) and I never noticed dithering on it (on the GC/wii on the other hand...); it also had a vertex shader unit; the fact that the GC lacked it meant it had to do some of those calculations on the CPU.
As for disadvantages (Xbox over GC), less textures and lights per pass meant in order to render a complex scene you would be halving the polygon throughput (also called the polygon trick) when compared to the GC who did 8 texture passes per pass, this happening on a platform whose polygon throughput couldn't match GC's from the get go; EMBM had more hit than regular bump mapping (whereas I've been told on the GC it was the oposite). The biggest advantage was bigger storage discs, and more RAM for bump mapping surfaces; these two no longer being aplicable to the wii.
Regarding Shader Model compliancy 1.1; although standard and more "widely known" for devs there's nothing you can do on it that can't be replicated on TEV pipeline (from shader model 2.0 onwards it's a different story); my point being that even shader model 1.1 compliancy would probably bite nintendo in the ass back in 2006 (when the wii launched); of course TEV pipeline didn't help though.
And yes, stuff like Normal Mapping and some other standardized effects were easier to implement on a Geforce 3, but GC/Wii also had it's share of custom shortcuts on silicon there, like the one for volumetric fog; they were just largely unknown/poorly documented.
.
