Since the sensor is so small in your Olympus, all it takes is that 5.8-16.2mm zoom to get the equivalent of a 36-100mm lens on a 35mm camera. That sensor will be much smaller than what's used on the Canon DSLR you're looking at. One thing that usually happens with bigger sensors is that higher ISO's are cleaner (less noisy, and noise looks a little like film grain).

Two things determine the angle of view - the focal length of the lens and the size of the film or image sensor. This is true of p&s digitals, 4x5 large format film cameras - anything. The smaller the film or sensor, the smaller the focal length you need to keep the angle of view equal. Because your Olympus' sensor is so small, the focal length is also very short. A 28-135 on that camera would give you a really narrow angle of view - and 5.8-16.2 would be extremely wide (to the point of being hard to do, optically) on that DSLR!