Most peoples experiences are the other way around, with the introduction of the C41 process prints and negative became more stable. Apart from the odd films poorly processed in the first place I've seen no noticeable deterioration of colour prints.
On the other hand all the prints offC22 negatives are fading, colours poor, washed out, they were rarely good in the first place. Older Kodachrome slides are no better, stability really came in with Kodachrome II.
I preferred Agfacolor prior to the introduction of Kodacolor II but the switch to C41 and E6 brought about a huge improvement in print and slide quality from all the manufacturers.