That's precisely the point....The Exorcist is a film. Made for the cinema. It neeRAB to be seen in the medium for which it was made.
Belive me, when the first time you see The Exorcist is in a 3/4 empty, cold, ramshackle cinema in Loughborough in 1980(..sorry Curzon, no offence..) it is the scariest thing you have ever seen in your life. No other film comes even close.
I bought it on VHS in the early 80's - before the "video nasties" ban, so it was a prized possession during the years it was banned from TV/Video, but I can assure you it is not the same on the small screen. I saw it a couple of years ago in a multiplex full of cynical teenagers, and once again my heart was pounding and my mind racing with genuine fear, not transient pseudo fear that most horror films induce.
See it at the cinema when you get a chance. Preferably on a Tuesday afternoon when there's hardly anyone else in with you.
;-)