50 Cent's Son Denies Dissing Him, But Says Dad's Music Sucks

50 Cent's son isn't shy about critiquing his father's music -- he says it SUCKS, but he also thinks everyone's getting the wrong idea about his own new track. 

Marquise Jackson tells TMZ his song, "Different," isn't a shot at Fiddy ... even though the track includes the line, "Lost my pops, he's still alive."