Now back to the discussion... The 808 is 2 years older than the Z2. No huge feat to get better benchmarks.
However, benchmarks aren't as good as side by side comparisons; are they? I think of benchmarks as a guide only - sort of a rough guesstimate.
Here's a side by side of the Z2 and a Lumia 1520... These two are only about 6 months apart in release.
Here's another showing Z2 vs Lumia 1020 (the direct successor to the 808) and these two are about 1 year apart in age.
Here is the Z2 vs the Lumia Icon which is about 3 months older. For Camera comparison, skip to 7:13.
Hopefully that provides some better comparisons over a dusty benchmark readout...