Meh, it really depends, sure consoles have little ram, they also work quite differently and are heavily optimised over Windows based gaming but theres few games alone that will push that much memory.
But thats the thing with Windows and a decent setup, you can do more than just "game". You can still play a lot of games with 2gb memory but doing so while leaving, Chrome, Firefox, a usenet program, VLC, and a lots of other apps open would be essentially impossible, on 4gb I can leave a load of stuff open but I do now and then hit the 4gb and watch my computer grind to a painful halt, did it only the other day with Lotro open and watching a film which started stuttering like mad.
That of course was down to Lotro and a memory leak so not quite fair
8gb would mean I could get away with more things at the same time, running one of my more intensive memory games aswell as something like photoshop doing something in the background is far easier on a 8gb machine than a 4gb machine.
Be honest, run 4gb, it you never run into a limitation or if its once every 3 months you find yourself needing to shut down 2 extra programs to run a game comftably, you really don't need 8gb. If you run into a 4gb limit frequently, like to do other intensive things in the background while gaming, buy the extra memory, more so while its cheap.
I ended up getting a new full 8gb of ddr2 when it was stupidly cheap, then at some stage got 4gb of ddr3 while not too expensive and sold the 8gb when the price was at its highest and ended up making money rather than losing it. I got another 4gb ddr3 when it was stupidly cheap and I might sell 4gb the next time it gets stupidly expensive.