Both Fujifilm X30 and Olympus E-P2 have 12.0 MP resolution sensors but Fujifilm X30's sensor is 2/3-inch (8.8 x 6.6 mm ) and Olympus E-P2's sensor is Four Thirds (17.3 x 13 mm ).
Since Olympus E-P2's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Fujifilm X30.
Below you can see the X30 and E-P2 sensor size comparison.
As seen above, Olympus E-P2 has a 3.9x Larger sensor area than Fujifilm X30. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.