I understand a 5970 GPU can do about 500Mhps, and it has almost 5Tflops. Scaling that up, the entire bitcoin network is equivalent to about 100 5970 GPUs, with about 500Tflops altogether. Half-a-petaflop! That's one tenth of the current best supercomputer, the tianhe-1 (see wikipedia) with a peak of 5 PetaFlops. Folding@home has about 5Pflops, BOINC about 4Pflops. (got all this from wikipedia).
FLOPS (Floating Point Operations Per Second) is irrelevant for Bitcoin, since SHA256 is entirely done by integer arithmetic. A Phenom II X4 does more than 7 GFLOPS, and does only 12 Mhash/s. You should look at MIPS (Million Instructions Per Second/Meaningless Indicator of Processor Speed) numbers. MIPS is not a very good indicator either, since a single instruction on some CPU can do the same as four on another, and there are pipeline stalls and whatnot. A super computer may or may not be good at this. If it is optimized for double precision floating point operations and high bandwidth between CPUs, it is probably not comparatively fast at pure integer algorithms requiring little bandwidth.
Real world performance of existing software on existing hardware is all that counts.
