I think it has to be played to judge its visuals. At the same time your on point regarding D3, HL2, riddick, conker etc, those have more 'stand out' effects which also age better.
UC liandri conflict also runs 60fps while having top-notch graphics at the time. I also feel some games just dont age as well as others do. Far Cry xbox was extremely impressive considering the hardware at the time. Today i think it looks bad in places.
D3 set the hardware atop of 6th gen, so did HL2, far cry insticts, dead or alive ultimate etc. Found this link awhile ago, some intresting (and amazing demo scene stuff).
https://medium.com/predict/pushing-the-original-xbox-to-its-absolute-limit-899b01e99133
Edit: Would be something if demo scenes did exist on todays consoles like it did during the 6th generation machines. The PS2 had many intresting ones.