This irritated me when I watched "Where Eagles Dare" recently. We learn at the beginning of the film that all the agents selected for this mission are fluent in German, but then all dialogue which should take place in German (when they go undercover) is actually shown in English, as well as dialogue which would be in English anyway (when they talk to each other or their commanders). Not only does this demand an unreasonable suspension of disbelief, but it's hard to follow what dialogue is in English-pretending-to-be-German, and what is in actual English.
On the other hand, in a film like "Cross of Iron" where all dialogue would really be in German but is represented in English, it doesn't really bother me. Watching a SW in Italian is a different experience to watching it dubbed, but doesn't seem particularly ersatz. Leone's answer to criticisms of Italians making westerns was that Hollywood had already done the equivalent to Italian culture with its heavily Americanised (& English language) Roman epics such as Ben Hur & Spartacus.
FYI, Memoirs of a Geisha is set in Japan & so should by rights be in Japanese, not Mandarin. The casting of mostly Chinese actresses in lead roles as Japanese characters is also typical hollywood silliness & possibly one of the reasons it wasn't filmed in Japanese. According to a documentary which appears on the DVD, communications on-set got a little chaotic, what with Chinese-English, Japanese-English and Chinese-Japanese interpreters used constantly by the cast & crew.