October 19, 2004 -- CRITICS said it wouldn't happen — but all-lib eral WLIB is seriously challenging talk-radio rivals WABC and WOR. According to Arbitron ratings released yesterday, WLIB thrashed WOR and nipped at the heels of top-dog WABC among the 25- to 54-year-old listeners advertisers chase. During midday, when both stations roll out their top guns — WABC's Rush Limbaugh vs. Air America's Al Franken — WABC is ranked 15th in listeners 25-54, followed closely by WLIB, which ranked 18th. WOR trails badly, finishing 27th in midday.