NEW YORK (Reuters) - With Valentine's Day just a week away, singer Whitney Houston's classic ballad "I Will Always Love You" has been voted the most popular love song in a U.S. poll. The signature song of the Grammy-award winning singer, who died suddenly a year ago, scored 38 percent of the vote among all adults in the Harris Interactive survey, and was the top pick among all divorced, separated or widowed Americans. Houston's hit from her 1992 movie, "The Bodyguard" was a cover of a 1974 song written and recorded by country singer Dolly Parton. ...