Why is the Fuji RAW file bigger than Sony and Olympus?

The Fuji RAF files from the X-E1 are all 26146816 bytes large. They are not compressed, or Fuji found a magical way to always come up with the same file size even after compression. Unlikely.

There have been threads before about the file sizes. Some cameras write out larger files than others, regardless of resolution. Cameras can record 12 bit data but write out 14 or even 16 bits.

To link the file size with the resolution of the image is, IMHO, quite far-fetched.

I have taken images with my D7000 and with my X-E1. We know that the D7000 images are compressed (lossless). After compressing the X-E1 image, the file size was smaller than that of the D7000, but I certainly wouldn't go around now claiming that the D7000 image has a higher resolution.