So PS4's GPU is equivalent to a 1GB 7850? It has 5GBS of GDDR5 dedicated to gaming, and 8GBs total. If you want to get really technical Guerilla Games said they're using 3GBs of video memory, so no its not all system memory. How much would it set you back to equip a PC with 8GBs of GDDR5? And please dont direct me to some off brand GPU you would never ever buy yourself.
Also the PS3's GPU was at best a dumbed down 7800GT
PS4 held its ground just fine against twin 7970s in the Digital Foundry BF4 test. You can say whatever you want for as long as you want, but if the PS4 was as low end and underpowered as you claim, that would not be the case.
First owner of a Playstation 4