There are two general ways to judge how a movie performs financially: a surprise hit, or a bomb. I don’t like to go by that rule, but it’s seemed to have gotten the best of me. A solid surprise came last fall with Oren Peli’s Paranormal Activity, a mega-low budget haunted house flick that ballooned to one of 2009’s biggest money-makers. This weekend Paramount shook the tree again with Paranormal Activity 2 and, no surprise, it had a pretty massive impact – an easy $20 million win on Friday, and the movie didn’t once drop more than 36% into the remainder of the weekend.

That stacks up to a $41.5 million weekend intake, far surpassing Paranormal Activity’s $19.6 million opening once it went wide, and the $21.1 million it killed Saw VI with this time last year. That of Paranormal Activity 2 is less impressive considering it was made on a $3 million budget in lieu of Peli’s original’s $15,000. It’s a great bow, obviously. How long it’ll last already in wide release, while Paranormal Activity started at a wickedly minimal number of sites and gradually expanded as word-of-mouth spread, is the question now at hand. Could Saw fans pummel it next weekend with a new 3D price tag?

Far away (practically the entire debut of the first Paranormal Activity) in second place was Jackass 3D, which fell 57.1% while grabbing another $21.6 million. Still, with respect to its own gigantic opening weekend, it deserves an indefinite “High Five”.

Summit’s Red dropped 31.1% to #3 with $15 million, $43.5 million in ten days; a less substantial second weekend drop than that of The Expendables, Knight & Day, and Killers…

Clint Eastwood’s Hereafter was boosted into wide release, playing at another 2,175 sites after a limited show last weekend, and debuted in fourth with $12 million. While not too great a start far as Eastwood is concerned, it is the highest opening weekend of screenwriter Peter Morgan’s career.

Aaaand rounding us out is The Social Network, declining 29.2% to #5 with $7.3 million and continuing to awesomely show its legs.

Here are the box office results according to studio estimates Sunday-

1. 1. Paranormal Activity 2…$41.5 million
2. 2. Jackass 3D…$21.6 million
3. 3. Red…$15 million
4. 4. Hereafter…$12 million
5. 5. The Social Network…$7.3 million
6. 6. Secretariat…$6.9 million
7. 7. Life as We Know It…$6.2 million
8. 8. Legend of the Guardians: The Owls of Ga’Hoole…$3.2 million
9. 9. The Town…$2.7 million
10. 10. Easy A…$1.8 million