The Very Best of Glen CampbellAmazon. com You could name scores of country artists whose catalogs go deeper than Glen Campbell's, but it would be next to impossible to name more than half a dozen singers who can match Campbell's countrypolitan best: "By the Time I Get to Phoenix," "Wichita Lineman," and "Galveston" (all late '60s crossover hits) are as sonically gripping and emotionally powerful as popular music gets. That's thanks in part to their songwriter, Jimmy Webb, but just