I'm sure they are out there, since for example Mario & Sonic Sochi... is on youtube even
Mario & Sonic at the Sochi 2014 Olympic Winter Games - Full OST ( Mario Themes Only ) - YouTube (
http://www.youtube.com/watch?v=BpDjbZ045ok)
Mario & Sonic at the Sochi 2014 Olympic Winter Games - Full OST ( Sonic Themes Only ) - YouTube (
http://www.youtube.com/watch?v=QUeeQHPTmfE)
Unfortunately I don't have either of them but I'd do some massive google and torrent searching with various tags/searches if I were you.
Edit: Yeah, didn't take long for Heretic for example:
http://www.doomworld.com/vb/showthread.php?s=&postid=1059198#post1059198 (Both MP3 and WAV links are working)