Bad for wrestling: He lowered the standard for technical wrestling.
If you look back at the WWF champions prior to Hogan, you will see a lot of technical wrestlers like Bob Backlund and the Iron Sheik (who was known as a human suplex machine a long time before Taz.)
When Hogan took over the mantle of WWF Champion, he played up the dramatic elements of his persona and matches. Rather than simulating an athletic contest, as pro wrestling had strived to do almost since its inception, Hogan's matches resembled something akin to a Superman comic book, with the beat downs and subsequent comebacks played up for dramatic effect.
Others followed suit and the 1980s were a rare time in wrestling when innovation in the United States didn't match that in other countries.