I dont have the experience of many on here, the problem for me has been the stakes and me been a child during the peak era.
By the time I was an adult, fruit machines were I felt very expensive to play if I remember they were 30p per spin or similar priced. On compensated machines could easily go a dozen spins with nothing other than pressing the spin button, so at 30p spin that was too much.
I had my fun in arcades on the cheap to play machines which also seemed to have much shorter winless streaks. But this was limited to summer holidays so once a year. Also my dad hated it so would have to sneak in when he wasnt watching.
What makes a machine fun is if you offered a feature game, the board very often, let me play that, try to make as many true gambles as possible on the features, and I can have fun whilst losing.