Acting was never Michael Jackson's strong suit.
The 'The Wiz' film (which was the most expensive film musical ever made at that time), not only it commercially flopped but also film critics did not like it at all, although Michael Jackson was in one of the lead roles.
Or, take his 'Moonwalker' film as another example: his fans watch it for the segments in which he sings and dances, not for the segments in which he acts.
Also, many of the singer's decisions (about portraying certain film characters) were rather laughable.
For example, his desire to portray the Spider-Man superhero character (in the '90s) did not make any sense at all.
Besides, his was too old at that time to portray such a superhero film character.
It appears that Michael Jackson used to publicly express his desire to star in certain films also because it was a way for him to remain always in the limelight (by, for example, having his name being talked about in the press).