I do not use Cannon nor have I used any of the lenses you mention. But it seems to me when reading your requirements and your possible list of solutions, that you more or less have the answer to your question in your posting.
If landscape and architecture are your main interests, then you can rule out all the lenses starting at 28mm and above. Wider is better and you probably will rarely use the 300mm length anyway.
If you want to photograph close up detail as well then the 18-200mm lens with macro would seem to be the obvious choice. Again I have no idea about the performance of this lens. I have the Nikon 18-200 VR lens which is great for convenience as I can cover most shots with just the one lens, but, whilst the quality is good it is not as sharp or fast as a fixed focus lens (obviously). And I don't have that macro facility either which you want.
Hope that helps and happy shooting!
