If Lego Batman 3 resists your attempts to run it in english without changing the system language, create this key using regedit:
Key = HKEY_LOCAL_MACHINE\SOFTWARE\WB Games\LEGOBatman3

That did the trick for me, I learned that by using ProcessMon for the executable.
The key might be already there and contain a DWORD value named "LanguageVal". Try to delete (or rename) that value or set it to 409(hex) or 1033(dec). These are the values used by the previous 2 games. For LB3 however it would work without "LanguageVal".

The previous 2 work in a similar way.
Lego Batman 1:
Key = HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Warner Bros Interactive Entertainment\LEGOBatman
"LanguageVal" REG_DWORD and set it to "409"(hex)

Lego Batman 2:
Key = HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Warner Bros. Interactive Entertainment\LEGOBatman2
HKEY_LOCAL_MACHINE\SOFTWARE\WB Games\LEGOBatman3


I understand that at least the GOG version of Lego Batman 2 comes with a language setter, so any information here might be obsolete :) This is just in case.