Is hd sapphire 6770 best for 720p gaming??

Yes it will play most games on high settings at that resolution. But by all means that is not the best card.

To max out those games at that resolution look at a 6870 or gtx560

my 5770=67770 was able to play everything quite well but was not able to max out settings

Otherwise the 5770 was quite good

To be sure, get a 7770. It's quite a bit more powerful than the 6770 and goes around for about $140.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Well i know a 560 can hold 60 fps on BF3 with ultra settings at 720p. In fact, i think the min you should look for at 720p is a GTX460, maybe OC it. Or a 7770 as auntarie says.

Though the only proven (from my experience) thing i can tell you is that a GTX 560 will max out anything at 720p and hold 60 fps (assuming your CPU doesn't come under pressure), and a 6770/5770 will manage "high" settings at 1366x768 quite well, so 60 fps at 720p shouldn't be difficult with the same.