You need to do some homework yourself, read some reviews, many reviews.
Decide what your price range is. What will benefit your computer, what will run in it.
Before you start yet another attempt at ati or nvidia post.
There are a couple issues when reviews compare the GTX 460 versus the AMD 6850/6870. Most will compare the stock speed versions of the GTX 460, but the majority of GTX 460's on the market are factory overclocked versions. The other issue is the confirmed image quality hack that AMD used in their recent drivers which pump up the performance numbers at the expense of image quality.
So if you compare a real-world GTX 460, one that comes factory overclocked with a nice custom cooler, with a comparable AMD card, the differences are minimal, and the purchase decision should come down to individualized tastes. As I am one who plays games that feature PhysX, for me the choice for an Nvidia card is obvious. It is also no question that the GTX 460 will perform DirectX 11 tesselation better than an AMD card, making the choice even more obvious for future-proofing your decision.
In terms of price/performance, you can easily find a nice GTX 460 for less money than a comparable AMD card. If you can find a MSI Hawk, an EVGA FTW, or Gigabyte Superoverclock you will be very happy.
One thing that almost everyone never mentions is power draw.
A stock 6850 draws about 15W less than a a stock 460GTX (thus still requiring a single PCIe connector). Heck even factory OCed 6850s still need just 1 connector. Msot OCed 460GTX suck anywhere from 160W (light OC) to around 180W (medium OC) to nearly 200W for the ultra OC cards like the EVGA FTW cards. Yes an the FTW will beat up a stock 6850 but it will suck 60W+ at full load, and this should be a consideration for many folks, especially if you plan on SLI down the road, as 120W is like adding an extra GPU to the mix.
I think there's going to be a problem because this card's bus is PCI-Express 2.1 x16(HD6850), my motherboard only supports PCI-Express 2.0 x16 will it work??
or I'll just have to go back to the gtx 460.
The gtx has finally arrived, I installed it and I'm loving it, I also upgraded my ram from 4GB to 6GB and no more lag games are smooth and perfect.
I appreciate all the help that I got from all of you guys and God Bless!