Eminem Sued -- Hey Lookin' Boy ... You JACKED Our Song!!

Eminem is NOT a rap God ... according to a MC who claims Marshall Mathers sampled his song "Lookin Boy" without permission -- and now he wants MILLIONS.

Raymond Jones -- a rapper from the group Hotstylz -- is suing Em and his record label for $8 million over the song "Rap God" ... which he says features a 25 second sample mid-track.

If you listen to the songs -- the music in question does sound strangely similar.

We reached out to a rep for Eminem ... so far, no word back.