The standard ranking of supercomputers is based on their performance in the LINPACK benchmark. The LINPACK behaver correlates well with the peak and it is usually 50-80 % of the peak.
This page is again a plot of the top 10+1 supercomputers that also shows the LINPACK performance (green columns). The y-axis reaches just to 200 PFlop/s.
The LINPACK benchmark is used as the main way of the assessment of the performance, because it is implementation of one of the principal method of the Numerical Linear Algebra - solving systems of of linear equations using Gaussian elimination.