Hmmm... I wonder why these chips have such strange differences? Maybe because they are COMPLETELY different chips.
Of course the Skylake 6700K crushes the Broadwell 5575C; it has the same number of cores, but they are 700MHz faster.
Of course the Broadwell 5575C crushes the Skylake 6700K in on board GPU; it has twice the execution units and has onboard cache. For graphics, the Skylake scored 2.363 per execution unit and the Broadwell only scored 1.856 per execution unit, even with the extra cache.
Basically if you aren't ever buying a graphics card, the 5775C is a decent choice. Or you could wait for the Skylake CPUs that have the Iris Pro Graphics 5800 as the integrated graphics, it has 72 execution units, with a cache.
i7 5775C, 3.3GHz, BOX : $377.00
Iris Pro Graphics 6200, GT3e - 48 execution units, 883.2 GFLOPS, 300MHz - 1.15GHz, 128MB onboard
i7 6700K, 4 GHz, BOX : $350.00
HD Graphics 530, GT2 - 24 execution units, 441.6 GFLOPS, 350MHz - 1.15GHz