...and to all a generic good-night'

First came generic foods. Then along came no-name laundry soap and sandwich bags. Now there's generic greeting cards. One publisher calls them ''a humorous takeoff on generic products.'' One generic Christmas card reads, ''Generic Season's Greetings Card'' on the cover, and inside - just ''Ho, ho, ho.''

It's possible to celebrate other occasions with a generic birthday card or a generic bon voyage card. Then there's an ''all-purpose generic greeting card'' with this message inside: ''Whatever.''