is video card memory have a lot to do with resolution?

Well, it depends. Resolution is only one factor.

A bigger factor is the resolution of the textures in-game. 320MB is more than enough for today's DX9 games, but as we move into DX10 we'll see more and more games that use super high-res textures to use 640MB, even 768MB.

And the 320MB card will never beat the 640MB one, unless, like you said, was overclocked. But you can overclock the 640MB one, as well. 

Are there any specific games that you play / are looking forward to playing?

oblivion

and crysis of course 

With the texture mods for Oblivian, you can easily fill up 320MB of memory.

If you have the money, get the 768MB 8800GTX. You won't be disappointed. Otherwise, I'd go for the 640MB and overclock it. You'll be glad you have the extra memory if Crysis uses the high-res textures as once claimed. 

i think buying a dx10 card now is so dumb.  unless your made of money, why not wait until it is necessary and then it will be 100 dollars or more less because of all the graphics cards soon to come outtigerballer

The time value of money my friend. To me (and many others) it's not worth 100 bucks to wait 6 months. It's worth the premium to have it for that duration imo. Also, the 8800s outperform every other card out there (presently) so you're getting performance and dx10 support. It's a great time to buy them imo.

im not made of money so i think ill buy a ps3 or 360 instead

thanks for all the advice 

PS3 is more expensive, and 360 is about the same.Baselerd

...and you need a HDTV to properly experience the great visuals. 

PS3 is more expensive, and 360 is about the same.Baselerd

I'd recommend a 360, since it's 2 hundred bucks or so cheaper and is actually graphically superior. (It has many more quality titles, too)