Since i've never could find it all at once, here's a combined guide. It's really easier than a piece of cake, i have no idea, why the game has to leave a player without a choice. English language pack is included in most cases(except for some brutal rips, i guess).
That solution works for license versions, in fact i took the solution to 2nd game from the official BioWare community.
Mass Effect 1:
Search for DefaultEngine.ini, somewhere around YourMEInstalDir\BioGame\Config\
Open it, find the string Language=*** under [Engine.Engine] section.
Replace any value you have (where I put the stars) with INT (which stands for 'international').
Save the .ini and launch the game.
Profit!
Mass Effect 2:
Search for sku.ini somewhere in YourME2InstalDir\data\ and open it.
There'll be VOLanguage=*** and TextLanguage=***, put INT instead of any language code you have in place i put the asterisks.
Save the .ini and launch the game.
Profit!
Mass Effect 3:
That's gonna be a *little* more complicated.
Could somebody test it without the 'download->overwrite' part, just by registry editing? I have a feeling that might work alone, but too lazy to reinstall the whole game.
Download the
language pack files and unpack them to your Mass Effect 3 folder with overwriting.
Run 'Regedit'. It's usually in the Windows main directory. Or just click 'Start=>Run" then type 'regedit' + Enter.
You need to find
32 bit Windows: [HKEY_LOCAL_MACHINE\SOFTWARE\BioWare\Mass Effect 3],
64 bit Windows: [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\BioWare\Mass Effect 3]
Change the values for 'GDFBinary' so it would end by '...\Mass Effect 3\GDFBinary_en_US.dll' and for 'Locale' to 'en_US' (without quotes)
Next step which you can skip if the required string doesn't exist:
32 bit Windows: find [HKEY_LOCAL_MACHINE\SOFTWARE\Origin Games\71402]
64 bit Windows: find [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Origin Games\71402]
If it exists, change the value for 'Locale' to 'en_US'
Save registry changes and launch the game.
Profit!
Note: the language pack will replace the 'Coalesced.bin', in case you had it modified it would be required to edit it once again.