ewwww. that is a tough one! well, let me start by saying that cg is my favorite restaurant in wdw, but the gf is my favorite resort. so let me ask a few questions....
are you staying at the GF or CR? if you are staying at one, then go to the other for dinner. you can always get the experience of sitting in the lobby having a drink at the gf or going to the roof/deck next to california grill to watch the fireworks at the CR another time. if you are not staying at either resort, then.....
have you ever been to the california grill before? i think it is very special because it is so-disney! it has very friendly service. the atmosphere is a complete split personality--loud yet sophisticated. the view is second to none. and the food. well i thought was even better than victoria and albert's. and then if you are there for fireworks or the water pageant, it is enough to send shivers down your spine! however, if you have been to cg, but not the gf, then pick a gf restaurant. the food will be good, the service will be attentive, and the overall package of lingering around the resort with other adults will be very relaxing. and besides, if you have been to cg, you would like to have a basis of comparison, right? if you haven't been to either, well then.....
i would lean towards the cg, but it really depends on what you are looking for. the gf will be more reserved, more quiet, more elegant, more romantic...between the music in the lobby and walks on the beach, it would be very nice.--even for 2 couples.
but if you are looking for the quinessential disney "adult" experience that is a little more lively, then go for the cg. i think the food there might be a little better too. i have definitely heard everyone on these boards talk very highly about cg, but not as much about citrico's. that is probably because fewer people go to citrico's though. good luck with your decision! it is a tough one, but i don't think you can go wrong either way.