Well, obviously, you'd still want quality glass that an 8MP APS crop DSLR won't outresolve, not just any old cheapy consumer lenses. My main point was to not assume that what held before for your higher pixel density, APS crop DSLR would directly translate to the Canon 5DMk2 w/out any consideration for such factors.
Still, if you want to ensure that your 5DMk2 (just as an 8MP APS crop DSLR) won't outresolve the lens when shot wide open (or near that), then yeah, you may still end up needing to go w/ all L lenses and primes to get that. OTOH, a higher pixel density, APS crop DSLR would probably outresolve any lens when shot at/near wide open anyway.
One other point I neglected before though is the edge/corner softness issue (besides outright vignetting/light falloff). You would certainly experience more of that w/ the same lenses on FF than on APS crop bodies -- maybe it's enough to offset the diff in pixel density in those parts of the frame.
_Man_
Still, if you want to ensure that your 5DMk2 (just as an 8MP APS crop DSLR) won't outresolve the lens when shot wide open (or near that), then yeah, you may still end up needing to go w/ all L lenses and primes to get that. OTOH, a higher pixel density, APS crop DSLR would probably outresolve any lens when shot at/near wide open anyway.
One other point I neglected before though is the edge/corner softness issue (besides outright vignetting/light falloff). You would certainly experience more of that w/ the same lenses on FF than on APS crop bodies -- maybe it's enough to offset the diff in pixel density in those parts of the frame.
_Man_