The i7 3770 is lga1155. This tech has been superceded by not only lga 1150 Haswell but also the lga1151 Skylake. As such it's demand has gone way down making current sales of lga1155 very expensive due to lack of supply. For all intents and purposes, the i5 6600k lga1151 is superior to the i7 3770k in every area except 1. The i7 3770 has HT, so is able to field upto 8 threads vrs the i5's 4 threads. This'll only be of any use in games which are well optimized for multi threads like BF4 or StarWars Battlefront. Most other games will run perfectly fine on 4 threads. Games aside, if you plan on some serious rendering, or other multi thread app that is high in cpu usage, the 3770 will win there too, using 8 threads vrs 4.
For a gaming system, general purpose pc, with what the lga1151 can bring to the table an lga1155 will be hard pressed to beat it and only then at oc speeds.