I don't really think its necessarily the size, but how they portray the character. THAT is what might make him intimidating and scary
I agree.... but as stated just above, size does come into play for most people. I'm 6' 2" and an avid weightlifter. I weigh 232 lbs. When I put on the coveralls at my height with broad shoulders, it does have an impact on people. When they are looking slightly up at me in most cases, and you throw my size in there, not to mention the great Myers costume, it's an overall attack of intimidation.
At my size, if a guy at 5' 9" and 190 lbs came at me wearing just about anything, Michael Myers mask or not, it wouldn't really bother me. (Not that I'm Hercules mind you.... okay.... I'm Hercules
) I'm sure there are many guys that size walking the planet who could whoop my @$$, but that initial fear and intimidation factor because of his physical presence would be missing.
Maybe that's part of Michael's strategy though... lure them in with a smaller body frame, then shock the crap out of them with super human strength.
I think about my size or bigger would be ideal, because it could provide more of a universal intimidation. There are a lot of guys my height out there.