DOOM 3, Halflife 2 : not on GC, but might be on GC2; MGS3, SC2 - don't know, but hey you've got to love or hate a SK production (MGS:TT, it's GC-only)... talking about revolutions - GC shows the most of it IMO this gen, but that's in term of gameplay, not graphics, you have to decide for yourself what's more important... that's not like not being good in the graphics department, on the contrary, but it's just not Nintendo's main focus. RE4 will be huge, if you haven't already done so - go check out some videos and screenshots

fyi doom3 is not going to ps2, and hl2 will probably come out for gc2/ps3...
Aside from the games you mentioned there is lots more (GC-only) in the GC's bright and shiny future... games like killer 7, metroid prime 2, zelda: ww 2, game zero, unity, baten kaitos (US), tales of symphonia (US), mgs:tt, re4 and more.... all of them are promising titles, so I'd say you don't have to worry about it.
Edit: best case scenario would be getting both a powerfull PC, and a GC, if you can afford them. PC is the primary and prefered platform for d3 and hl2 IMO