A somewhat more fair comparison would be V8 vs. PyPy, Rubinius/RuJIT, HHVM, and LuaJIT. LuaJIT and V8 would likely still come out on top due to the amount of work and sheer excellent engineering put into the compilers (and in LuaJIT's case, also the interpreter), but PyPy's performance should be a lot better than CPython's for these benchmarks.
I also imagine (though am mostly speculating) that a benchmark involving a full-stack frontend framework like Angular or Ember, with hundreds or thousands of JS objects and lots of DOM manipulation, should put V8's performance a bit closer to CPython's.