There is a large difference between the quality and flexibility you will get from a dSLR or a 4/3rds camera and a a S95. That isn't to say you cannot produce outstanding shots with a compact; people have produced thousands of great shots on compacts.
What I would suggest is that the physical limitations of sensors and of the lens does have an effect on the overall aesthetic and technical quality of the photo. Or else people wouldn't invest in higher end camera gear. You could argue rather persuasively that if you want really great landscapes, large format photography produces the best results, because of the availability of movements and precision calibration available to the photographer. But yet, I see a TON of great work done on 35mm, far better than I could ever hope to achieve as I am not a very good photographer (yes, the person handling the tool does matter).
But that much said, the good thing about landscape photographer with even a low-end DSLR or a 4/3rds outfit, is that they are quite capable. There are plenty of good lens choices, some of them downright affordable, particularly if you purchase lenses that's aren't pushing the extremes in aperture. (i.e. a "fast" lens that can control a very shallow depth of field)...
The downside with most 4/3rds cameras and dSLRs is that the super wide angle lenses are expensive. This is made worse by the fact that the sensor sizes (with the exception of full frames), generally changes things a bit - on a 4/3rds camera you double the focal lengh. Thus a 14mm wide frame on a 4/3rds would be come 28mm equivalent to a full frame 35mm camera.
As Franco and Rick point out, there are compelling reasons to pick a better camera if photography is your passion. However, and this is crucial to this discussion, the camera that remains in your backpack is worthless. The camera that is used will capture photographs and thus has value. If you are recording images from a journey, I would say that a compact is a great tool. I've carried the full dSLR with me (and a couple of lenses) and I found I didn't use it much because it involved taking off my pack and unloading it. The compact, while nowhere near as fully functional, is used often, because I slip in in and out of my pocket. Ulimately my goal was hiking rather than photography - and thus, I stuck with the compact for now. But I am very interested in a Olympus first generation PEN because they are so inexpensive and can be manually focused with old prime lenses.