The humans of Yes, if this weekend at the box office were a movie, it would be a less than super-imaginative sequel. Once again, “Avatar” ruled at the U.S. box office. As seen on the mighty weekly chart of Box Office Mojo, James Cameron‘s mythic, politically pointed, science fiction adventure once again took the crown with an estimated $48.5 million for Fox. That’s a drop of only 29.2% in its fourth box office weekend, following a huge and long prior holiday weekend. No doubt helped out by those premium 3-D and Imax ticket prices, it also enjoyed the nation’s highest per screen average at about $14,173. In the relatively short time I’ve been doing this, I don’t think I’ve ever seen that happen on a movie’s fourth week.

As reckoned by the Mojo, “Avatar” is the now the #1 domestic moneymaker for 2009 and the #7 cinematic cash cow of all time, with a very definite bullet considering its signs of considerable ongoing strength. In others words, this is a movie people actually enjoy, not merely tolerate because it offers enough explosions to distract them for a couple of hours.

On the other hand, just to keep things in perspective, adjusted for inflation, “Avatar” is still a 56 steps down from the all-time ticket seller, “Gone With the Wind.” On the other hand, lest James Cameron should be threatened by any momentary bouts of untoward humility, at least in terms of raw cash he really is box office king of the world right now. “Avatar” is already the #2 grosser of all time at $1.331 billion, $500 million and change behind “Titanic” — written and directed by you-know-who. Can I still wish Cameron had brought in a competent wordsmith/dramaturg to smooth out the very rough edges on both films?

As for the second and third place positions, we had another photo-finish in which Warner’s “Sherlock Holmes” narrowly edged out Fox’s “Alvin and the Chipmunks: The Squeakquel” by a rodent hair. The world’s greatest literary detective brought in just a hair more than an estimated $16.6 million and the musically inclined woodland creatures managed an estimated $16.3 million. With the holiday weekends at an end, they both exhibited more typical drops for typical Hollywood product, with “Holmes” dropping by 54.6% and “Chipmunks” by 53.7%.

As predicted, a violent/satiric spin on the peaking monsters of our moment, vampires, “Daybreakers” came in at very decent 4th place showing with an estimated $15 million for Lionsgate. Another newcomer placed #6, after the AARP-friendly rom-com, “It’s Complicated.”  That was “Leap Year,” a movie I’m embarrassed to admit slipped my mind on Friday’s report but apparently not the ever less demanding viewers of romantic comedies.

Amy Adams and Matthew Goode in

Expectations were low — single digits said jolly Carl DiOrio — for this critically disliked rom-com with apparently mild “tracking,” despite the presence of the wondrous Amy Adams. By managing a double-digit showing, it will do no harm to either her career or that of costar Matthew Goode, the rather interesting actor best known as Adrian Veidt in “Watchmen” and also Colin Firth’s dead lover in the probable Oscar nominee, “A Single Man.”

Conversely, schadenfreude fans rooting for the non-stardom of Michael Cera got some ammunition with the disappointing numbers for “Youth in Revolt,” which earned an estimated $7 million. That result will not be music to Harvey and Bob Weinstein’s already reputedly fiscally troubled ears, considering the film was supposed to crack double digits.

Also, it’s a bit of an embarrassment to me because I mentioned the possibility of a surprise in the opposite direction. Still, it should be noted that comedy based on a series of books by C.D. Payne was in a relatively modest 1,873 theaters, as opposed to 2,511 for “Leap Year,” and it’s per screen average of $3,737 is not an embarrassment.

Heath Ledger in Among limited releases, though Box Office Mojo apparently failed to track it, “The Imaginarium of Dr. Parnussus” the Terry Gilliam-directed fantasy film starring the late Heath Ledger, expanded to 550+ theaters last week and appears to have actually been the #12 movie in the country with, as per Nikki Finke and Carl DiOrio an “acceptable” $1.7 million for distributor Sony.