Please remember 2 principles if you would like to be ranked higher: 1. The logo needs to be printable and recognizable also on small items (e.g. a pen). If I imagine entry #6 or entry #8 be printed in 3-4cm width, then the skyline is hardly seeable / reconisable. Also line width is important here, therefore is entry#6 (although a nice logo) in practice not acceptable. 2. We like capital letters like in your entry #8 best.
I'm trying to simplify the skyline, using most "unique" building shape. With simpler skyline, it's easy to recognize, event in small size. (skyline's detail is simpler than text itself. so, if we could read the text, its easy to recognize the skyline). 2 process color (cyan-gray/black) is great. nice but cheap. I'm in this business too...