BERLIN — “The Avengers” may be unbeatable, but not without its 3D shield.In Germany, as everywhere, the pic has been No. 1 at the box office, but a closer inspection reveals that the No. 2 film, the 2D “American Reunion,” has consistently sold more tickets, beating”Avengers” by 118,000 admissions in week one, and 111,000 in week two. Week three was much closer, with only a 27,000-seat gap. The 3D upcharge for “Avengers” was the deciding factor each week in the superheroes climbing to the top of the B.O. This is not the first time an upcharge has propelled a 3D film to the top in Germany. Last September, Paul W.S. Anderson’s “Three Musketeers” had the territory’s best cume ($3.34 million on 233,153 admissions) in its first week of release, but the majority of German moviegoers opted to attend local 2D romantic comedy “What a Man” ($2.64 million/251,588). “Three Musketeers” still topped the box office in its second week in the territory ($2.78 million/202,915) but romantic laffer “Friends With Benefits” was better attended ($2.46 million/243,112). The same thing happened in November: With the 3D “Immortals” ($1.77 million on 119,207 admissions) enjoying its second week at No. 1, followed by 3D pics “The Lion King” ($1.43 million/108,774) and “Tintin” ($1.2 million/101,272), a re-release of the 2D “Twilight: Eclipse” ($1.1 million/149,597) in the runup to “Twilight Saga: Breaking Dawn — Part 1″ sold the most tickets, by a whopping 30,000. In neighboring Austria, contrary to almost everywhere else in the world, “The Avengers” never reached No. 1 all, beaten each week, in both admissions and grosses, by “American Reunion” as well as the “Dark Shadows” debut May 11.