Marketers pitching products and services to kids might be surprised to know just how much youngsters read. Even in this age of virtual everything, large numbers of young kids still love good, old-fashioned magazines. According to the 1996 Roper Youth Report, published by Roper Starch Worldwide Inc., a market research firm in New York City, 8 percent of kids as young as age 6 cited Highlights for Children as their favorite magazine. Other winners for older kids (ages 8 to 12) were Sports Illustrated for Kids, TV Guide, National Geographic and Nickelodeon. Even better news: Magazine readership generally increases with age, and boys and girls show similar preferences for publications up to the age of 12.