That depends on what you are doing. Plus take into account performance per dollar. It's so wrong when people compare an I7 975 to the AMD 955, you don't use stock clock speed as reference to compare you use price. It's I7 920 VS AMD 965 currently that are the same price range. And in gaming, the 965 has an edge. Actually, if you left it stock clock speeds, the 965 would probably beat the I7 in everything. 2.66 VS 3.4 GHZ, huge difference especially with gaming benchmarks and real world gaming as well.
My friend, i7 920 @ stock speed does beat AMD 965 @ stock speed most of the time
Here some reviews
http://www.tomshardware.com/reviews/phenom-x4-965,2389.html
http://www.guru3d.com/article/phenom-ii-x4-965-be-processor-review-test/%5Dsource
http://www.bit-tech.net/hardware/2009/08/17/amd-phenom-ii-x4-965-black-edition-review/1
nandtech.com/cpuchipsets/showdoc.aspx?i=3619&p=1
In gaming they perform about same, but i7 920 is do much better in other things. And remember that all current games can't use more than 4 threads.