Link -- NEX-5N & Zoomar Kilfitt Makro 90mm f2.8. Click for larger.
I have noticed that from the Canon 2Ti, some of my favourite old lenses, like the Kilfitt Makro 90mm f2.8, did not work very well on high density sensors. Same problem on the 7D. What looked very nice on the 11 MP 1Ds and the 5D classic full frame cameras look very lifeless and boring on the T2i and 7D. Even tried the Angenieux Speciale Cine 210mm f2.8. Pictures looked much better on the 5D than on 2Ti/7D.
I think that older lenses just do not have the resolving power for today's high density sensors. They produce beautiful pictures on older cameras but not so nice on newer ones. This is not scientifically proven, of course, so I could be wrong, but pictures do look duller and less sharp on newer cameras. On the other hand, lenses like Carl Zeiss Distagon 35mm f2.8 (Contax Mount), and 60mm f2.8 S-Planar Makro perform about the same on most cameras. So, perhaps, there is a connection.