Never particularly known as a mecca of great fiction, Ms. Magazine nonetheless, in this retrospective, comes up with a pair of very fine stories, a trio that's almost as good . . . along with the more predictable others: recastings of social arguments into journalism-as-fiction. Best are Doris Lessing's ""Not A Very Nice Story""--which regards adultery from a vantage point akin to that of the Old Testament God (analytically unsparing); and Fanny Howe's ""The Right Thing""--which exposes wrenching cruelty under the guise of personal enlightenment. Margaret Drabble's ""A Success Story"" takes a mischievous, perverse slant on ""what women really want,"" sharing secondary honors with Sally Gearhart's tribal and inventive ""Krueva And The Pony"" and Mary Heaton Verse's 1907, Jamesian ""The Quiet Woman."" And the rest is, unfortunately, much poorer: Alice Walker, Hilma Wolitzer, Mary Gordon all writing well below their optimums; Jane Shapiro, Lynda Schor, and Frenchy Hedges hobbled by amateurish execution. A few diamonds, then, in a generally rough collection.