Weather varies widely around the world, so no two wine regions fare exactly alike. In 1989, record heat produced large, ripe harvests throughout much of Europe, resulting in vintages generally considered fine. But the same year brought rains at harvest in California's North Coast wine country, causing a vintage that many buyers avoid. And even there, much depended on whether individual producers picked early, bringing in grapes before the rains came. Vintage charts also depend on the knowledge and skill of the author, and opinions may vary widely.
Some vintages are simply hard to like.
I've rarely met a 1984 Bordeaux that I enjoyed, and few enthusiasts would speak highly of 1991. In my opinion, vintage charts offer the consumer a helpful guide, but it's best not to rely on them slavishly. Further, avoid charts that paint with too broad a brush. But if you trust a particular critic's ratings, then it makes sense to note his comments on vintage. One reliable guide is the Hugh Johnson Pocket Encyclopedia of Wine , which rates thousands of specific wines, gauging the quality of the vintage for that wine and advising whether each year is ready to drink or requires more time.