Michael Myers became an icon after the release of Halloween, which is still considered to be the slasher movie.
I think the reason Myers struck such a chord is because he was not some supernatural, super-powered demon from hell; just an institutionalised psychopath with absolutely no concept of right or wrong. When he kills his victims, it is not with gleeful malevolence, hacking them to bits with violent fervour; he’s much more like a little boy pulling the wings off an insect. It’s Donald Pleasence as Dr. Loomis that makes the film however, as a criminal psychiatrist who is clearly terrified of his charge is a very powerful image; but at the same time it’s very difficult to take slasher movies seriously these days and it has dated somewhat as a result. The vast number of imitators, spoofs, post-modern “re-inventions”, not to mention it’s own increasingly dreadful sequels have seriously diluted the impact of the film, and the Japanese have definitely surpassed Hollywood when it comes to creating quality horror.
But Halloween is the original, and still easily one of the best.