That was his origin. It would really be a 90-120minute story on bounty hunting. Over and over shooting a rocket from his wrist, jet pack away and using a net and some darts. Star Wars is about Jedi's. No Jedi's, no fun.
The reason why he's popular is that he wasn't much in the film and he had the above mentioned jet pack and wrist rockets and the kids back then who are no all 30-40 year old or so thought that was super cool and "who the hell is this guy". I'm not sure a lot of people are heavy on the Boba love from growing up with the prequels and a stand-alone movie about him would just ruin the mystery.
Think about what Fett did in the movies. He asked Vader if he could get Solo to collect the bounty (didn't even capture Han himself). He's with Jabba when the gang is about to be eaten by a sarlacc, but they escape, and whilst he tries to stop them he fails and dies.
In Attack of the Clones he watches his father's head get chopped off, screams and cries (I think). Basically in all movies he's been a total failure yet he's seen as some kind of a badass super villain.
You could make a bounter hunty film using any bounty hunter really. There are loads of them in the universe. Ones where the beginning and the ending hasn't been revealed.