Here's my take;
Avatar: You have to spend money to make money
Well haven't seen it yet, but everyone's raving about it for the effects, but that's because it's something new, Hollywood learned this lesson with the Matrix and will screw up like they did with the Matrix, by putting it in every movie.
District 9: Then again, you don't have to spend all of it to make an effective sci-fi action flick
Have a big name producer and actually hire a writer instead of chaining a chimp to a typewriter is the real lesson.
The Hangover: R-rated comedy starring mostly unknown but truly funny actors can lead to great things
American Pie anyone?
The Hurt Locker: Iraq-themed movies work and work best with a female director handling the reins
Won't comment, since I haven't seen the movie
Ice Age 3: Don't underestimate the power of the non-U.S. box-office(it made almost 700 mill WW)
Harry Potter anyone? Chronicles of Narnia? There are plenty of examples of this.
Inglourious Basterds: QT and Harvey Weinstein are a lethal duo
As long as Tarantino makes an homage movie to a genre people care about it'll be gold, no one cared about Grindhouse movies to start, Nazis and WWII usually have a good track record
Paranormal Activity: Actually, you don't have to spend any money at all, really
Blair Witch taught us this 10 years ago
Precious: Sundance can still generate buzz
Oprah can still generate buzz
Sherlock Holmes: Never underestimate star power, even in Victorian garb
Star Trek: Truly fresh reboots can reignite a franchise, pulling in new and old fans alike
Bolding them both since it's the same thing a reboot that has a fresh take on the source material. I don't think Sherlock Holmes' success is star power, it's intial franchise name recoginition in new shiny packaging.
Taken: Liam Neeson is a viable action star
Liam Nesson was a large part of the action in Phantom Menace
The Twilight Saga: New Moon: Vampire fever is only beginning
This is a very fast burning candle, Twilight = The Backstreet Boys, 'NSync, New Kids on the Block....
Up: Pixar always for-the-win
That's a new lesson? Hasn't every Pixar movie been a hit?
Zombieland: Indie actors vs. the undead = Fanboy delight
The three younger leads in the movie are working hard to become non-indie actors, it was also released at exactly the right time, a somewhat fresh take (since Shaun of the Dead really did do it first) on the horror genre around Halloween, perfect timing.