TFLOPS is not the only way to compare two gpus. That would only be good if you were going to do, well, floating point operations. For example, a 5870 can do more FLOPS than a 7870, but the 7870 is quite a bit more powerful in gaming.
The PS4's gpu is somewhere between a 7850 and 7870. There was nothing that powerful on the market back in 2006. IIRC the ps3's gpu was similar to a 7900GT, which wouldn't be capable of playing and AAA from the past couple years at decent settings on a PC.
The cell is 2 Teraflops the RSX was 400 GFLOPS. Now with the Apu we have that switched. The radeon itself 1.84 Teraflops. With uma and 16 times the memory.
The ps3 is most long in the tooth in regards to memory. This has lead devlopers to leverage the hard drive to help memory constraints.
To me memory is the big advance over current gen. Something that developers have been saying for the last two generations