Captain Sim has both a 757 and 767. I have only seen the 57, and it seemed to be a frame whore. Captain Sim does very well with their aircraft. They have very nice features and great detail. I know there is a company called LevelD that makes at least a 767, possibly a 57 as well. Google LevelD 767 and you will find it. I have heard nothing but great reviews on the LevelD stuff.
As far as looks, Ground Environment Extreme looks amazing. I have yet to try it, but you should definitely look into it. If you fly in an area more than others, try finding Mega Scenery for that area. If you like photo real scenery, but want it for free with the cost of losing your trees and buildings then try TileProxy.
Let me know if you are looking for certain aircraft or addons. If I have heard of any Ill let you know. Back to the 757 and 767, Project OpenSky does a a lot of commercial addons for FS, they are freeware and often dont have a virtual cockpit though.