So, among the top 40 of the decade, 90% were "unoriginal." How does that compare to overall?
So far, there have been 94 live action, non-documentary movies that have earned at least $15 million dollars domestic in 2009. But original are much more common in the top tiers of this list than in the other list (note that this is domestic grosses where the other list was worldwide grosses; worldwide tends to filter out comedies).
Anyway, curiosity sated. Data in the spoiler.
In a nice bit of serendipity, exactly half (47 are original screenplays). There's room for quibbling on some.
Spoiler:
1. Transformers: Revenge of the Fallen - Sequel, TV/comic book adaptation
2. Harry Potter and the Half-Blood Prince - Sequel, book adaptation 3. The Hangover - Original 4. New Moon - Sequel, book adaptation
5. Star Trek - Sequel, TV adaptation
6. X-Men Origins: Wolverine - Sequel, TV adaptation
7. Night at the Museum: Battle of the Smithsonian - Sequel 8. The Proposal - Original
9. Fast and Furious - Sequel 10. 2012 - Original 11. G.I. Joe - The Rise of Cobra - TV/comic book adaptation 12. Paul Blart: Mall Cop - Original
13. Taken - Original
14. Angels & Demons - Sequel, book adaptation
15. The Blind Side - Book adaptation
16. Terminator Salvation - Sequel 17. Inglourious Basterds - Original 18. G-Force - Original 19. A Christmas Carol - Book adaptation 20. District 9 - Original
21. Watchmen - Graphic novel adaptation 22. Paranormal Activity - Original 23. Couples Retreat - Original 24. Public Enemies - Based on historical events (not sure how I would count these)
25. Julie & Julia - Book adaptation
26. He's Just Not That Into You - Book adaptation 27. Tyler Perry's Madea Goes to Jail - Original
28. The Ugly Truth - Original 29. Knowing
30. Hannah Montana The Movie - TV adaptation
31. Where the Wild Things Are - Book adaptation 32. Zombieland - Original
33. Hotel for Dogs - Book adaptation 34. Law Abiding Citizen - Original
35. I Love You, Man - Original
36. Obsessed - Original 37. Race to Witch Mountain - Remake, book adaptation
38. The Final Destination - Sequel
39. The Taking of Pelham 1 2 3 - Sequel, book adaptation
40. Friday the 13th - Remake 41. 17 Again - Original
42. The Time Traveler's Wife - Book adaptation
43. Bruno - TV adaptation 44. Bride Wars - Original
45. The Haunting in Connecticut - Not sure how to categorize, based on silly claims of truth. 46. Ghosts of Girlfriends Past - Original take, but obviously inspired by off a book.
47. Funny People - Original
48. Tyler Perry's I Can Do Bad All By Myself - Original 49. My Bloody Valentine 3-D - Remake
50. Land of the Lost - TV adaptation
51. My Sister's Keeper - Book adaptation
52. Underworld: Rise of the Lycans - Sequel
53. Confessions of a Shopaholic - Book adaptation 54. Year One - Original
55. The Unborn - Original
56. Drag Me to Hell - Original
57. Orphan - Original
58. Duplicity - Original 59. Surrogates - Graphic novel adaptation
60. State of Play - BBC mini-series adaptation
61. Notorious - Biopic
62. Precious - Book adaptation
63. The Pink Panther 2 - Sequel 64. Old Dogs - Original 65. All About Steve - Original 66. Halloween II - Sequel, remake
67. The Informant! - Book adaptation
68. The Last House on the Left - Remake 69. (500) Days of Summer - Original 70. Push - Graphic novel adaptation
71. The Soloist - Book adaptation
72. The Men Who Stare at Goats - Book adaptation 73. Ninja Assasin - Original 74. The Stepfather - Remake
75. The Uninvited - Remake of South Korean film
76. Saw VI - Sequel 77. Dance Flick - Original 78. The International - Original
79. The Fourth Kind - Original
80. Observe and Report - Original
81. Fighting - Original
82. Love Happens - Original 83. Fame - Remake 84. Shorts - Original
85. Gamer - Original
86. The Invention of Lying - Original 87. Inkheart - Book adaptation 88. Fired Up - Original
89. New in Town - Original
90. Jennifer's Body - Original
91. Imagine That - Original
92. Adventureland - Original
93. A Perfect Getaway - Original
94. The Goods: Live Hard, Sell Hart