No one is completely qualified to put together this list, because no critic sees every awful movie, but based on the fact that my editor at MSN sent me to "Cop Out," "The Tooth Fairy" and "Jonah Hex" this year, I more than familiar with the genre of total stinkers.
But you may quibble with my list. You may say, what of "The A-Team," "MacGruber," "Marmaduke," "The Prince of Persia," "The Human Centipede" or the "The Expendables"? You may have suffered through them, but I did not. Speaking of, I left two movies at the halfway point this year -- which obviously I can't do if I'm reviewing, and I try not to bolt from more than one a year, just so it doesn't become a habit -- which means that I can't include them on this list.  But I feel pretty good about feeling pretty bad about the following movies.  
10. 'Sex and the City 2'
9. 'For Colored Girls' 
8. 'Jonah Hex'
7. 'The Last Song'
6. 'Kick-Ass'
5. 'The Tourist'
4. 'The Back-up Plan'
3. 'I'm Still Here'
2. 'Inception'
1. 'The Last Airbender'