We've all heard the tales about King Aerys and his crimes, but they seem to paint Robert Baratheon in a conveniently good light, considering that he usurped the throne. Was he really so much better than Aerys, or do we just think that way because of years of propaganda?
You first understand why Robert waged his war against Aerys "the mad", Robert was to wed the sister of his good friend Eddard, Lyanna. Before they married Lyanna was kidnapped by Aerys's son Rhaegar, Eddards brother Brandon was in Riverun at the time and rode to kings landing and called out for the death of Rhaegar, he was imprisoned for ploting to kill a member of the royal family. When Brandon, his farther, rode to kings landing to answer for his sons crimes he was hung upside-down over a fire while his son Brandon was placed into a device that strangled him as he struggled.
Aerys was also known to have a huge sexual facination with fire, all excutions where done by burning the accused to death.
He burned to death every member of house Hollard, which seeked to usurp the throne from him.