No they don't. Olympus and Pansonic use 4/3 and Sony and Pentax use APS-C in their lower end bodies. Sony has had 35MM frame sensors in the A850 and A900 and Pentax has the 645D medium format digital camera. Sony sensor technology has been behind a number of the 35MM frame sensors used in Nikon high end cameras. Sigma uses sensors similar to APS-C size too and so do Fuji and Leica uses larger sensors too.
DR in the final picture is also not only connected to photo-detector surface area but also the technology used in the sensor and the processing algorithms used too.