I gotta agree with the above posters, if i HAD to pick one, it'd be MOH Vanguard.
COD 3 when it first came out, i found to have very fast controls, compared to far cry (horrid on wii) and red steel (slow turning arc even when turned up).
I got used to COD3, but, i did find the controls sometimes too quick for its own good. Once MOH came out, i found the controls in that game more suited for the wiimote and it makes the game a better experience overall i think.
Graphically, well, COD3 is better, but MOH isn't a "bad" looking game, its just not a great looking one either.
So yeah, if you gotta buy one, get MOH, if you got a modchip, get both.