If you are talking about image quality the D7100 has better image quality than an A77 bar none. It renders colors better, has better dynamic range and much better ISO performance - rendering less noise and holding details much better. After ISO 800, maybe 1600 for small prints the A77 is almost unusable. The D7100 is pretty usable to ISO 3200 and some would argue 6400.
While both have excellent AF systems, the Nikon has better focus tracking thanks to having almost 3x the focus points and much better frame coverage.
The Sony does have better FPS, 8 vs 6 ( and a 12 FOS burst mode that some find more useful than others). The Sony has a better buffer, but not by much and not as good as even the D300s. The Sony has an articulating screen, the Nikon is bigger and has more resolution. The Sony does have in camera stabilization which Nikon has eschewed in all bodies - I have never heard why.
Finally, the Nikon has an OVF while the Sony has an EVF. An EVF is a deal breaker for many still image photographers and no one can seriously argue that even the world's best EVF is as good as the OVF in the Nikon.
As for lenses, The 17-55/2.8 from Nikon remains an excellent professional grade lens, even though it is dated now, the optics compete with anything in this range on APS-C cameras. The Sony may be marginally better, but its gains are lost by being attached to a camera with inferior image quality. I can't really defend Nikon here too much on DX lenses though - they have dropped the ball by not keeping up with the demand. An update to the 17-55 with VR should have happened by now.