It's not as simple as how many flops can you do. The PowerPC Top500 are created specifically certain types of workloads and are designed by to ran at 100% 24/7. The idle power consumption of those platforms is ridiculous. Super computers are nothing like computers in normal datacenters. Datacenters have large swings of computational usage and do a lot of VMs. Super computers have constant load and run bare-metal for the most part with highly optimized OS's with kernel schedulers that schedule time slices in quantums of minutes instead of milliseconds.
And yes, AMD has great peak flops and can compete with Intel in this area, but AMD's design is biased more like a GPU than a CPU and takes a big hit any time you need to do thread synchronization. Higher latency to flush a cache-line, which is highly detrimental to synchronized performance(Amdahl's law). AMD wanted a large exclusive cache instead of a smaller low latency inclusive cache. ARM is great if you only need a bunch of weak CPU cores. Below 1Ghz, ARM is slightly ahead of Intel. Around 1ghz, ARM runs into efficiency issues and suddenly they draw more power than Intel and only similar performance at best. ARM does beat Intel in some niche workloads, but the same can be said about pretty much any CPU.