Once upon a time, it was Elizabeth Taylor. Now it’s Daniel Radcliffe.La Liz created mob-scene pandemonium on West 46th Street when her new hubby Richard Burton appeared in “Hamlet” at the Lunt-Fontanne in 1964. She then repeated that mass appeal in front of the Martin Beck Theater on West 45th Street for her Broadway-debut run in the 1981 revival of “The Little Foxes.” Today, Radcliffe is producing Liz Taylor-size crowds outside the same theater, renamed the Al Hirschfeld, with his turn in “How to Succeed Without Really Trying.” Two hundred fans gather for autographs on a nightly basis, with the numbers nearly doubling for weekend perfs. All those youngsters who couldn’t see him in the buff in “Equus” have found willing parents to buy them tix this time around. Three cops keep car traffic moving on West 45th and two Jujamcyn security guards make sure there’s an escape route for the show’s other thesp. Pandemonium should build right up to the summer preem of the final “Harry Potter” pic, when Radcliffe departs for London after the July 6 perf and returns to the tuner for the evening show July 9.