Anything I've looked at on Archive.org (mostly video but some audio) has the original uploaded file plus trascodes into Ogg Theora and H.264. So even if it is "transcoded crap", you're given the option of the original. Which makes sense when you've got "archive" in your name.

Wikipedia may only serve free formats, but they'll make use of stuff from Archive.org so you can click through to the original if it's there.