In general I am not given to using standard zoom as I find the image quality falls below that which is obtainable from so called fixed length lens and many have the apertures varying as you zoom which messes up manual and spot metering readings.
As I use a tripod making small adjustments to frame the image and keeping it all level is not a big deal to me
For general landscapes I use the Olympus Zuiko 28mm F2.8 pictured below a lot liking its colour renditions and ease of use. The construction of Olympus's own lens is extremely good being all metal.
Another good feature of them is the aperture settings are at the front making for rapid focusing and metering while you are looking through the viewfinder.
I bought this lens in September 1996 for the OM10 when I was test driving it.
My first love though is the 35mm F2.8 which I bought around 2002 from Camtech over the phone.
I found whenever I used a zoom most of time I was using around this focal length because it's ideal for travel photograph and has less of a problem with converging verticals when you photograph buildings. Although the edges wide open are slightly soft they come in by F8 and it looks really good. Some say they found the contrast a bit low but honestly I've never found it on the films I've used (Velvia 50/Reala 100).
I got mine boxed with the case and thin front cape used and love it.