But not all games are backwards-compatible, largely for licensing reasons. I miss playing Rock Band Blitz, for instance (but the licensing for the songs ran out years ago). I can only run that game through an original Xbox 360.
Neither PS Now nor Xbox BC have access to SSX Tricky (likely the music licencing again) so both of those services can f**k off. Xbox does have SSX 3, which is something, at least, but it's no Tricky