As Ignacio said in his answer the image will not look good in any resolution except the native resolution. However, one potential work around is not to run the game in full screen mode but in windowed mode. Yes, the image area will be smaller doing this but you will have crisp images in that smaller area.
So in summary here are your options:
- Live with a blury screen
- Live with playing in windowed mode on a smaller section of your screen
- Lower the quality settings other than resolution (AA, shadows, reflections, ect...) and play at native.
- Buy a better video card so you can play the game at the monitors native resoltuion
- Buy a better monitor that does better interpolation at non native resolutions.
Edit: I found this review of the monitor, it says the interpolation options may be able to be changed via software
The interpolation behaviour of the ViewSonic VX2235wm can not be
modified on the hardware side. Resolutions which do not correspond to
the native 1.680 x 1.050 are therefore always interpolated on full
screen. The result is that resolutions with a page format other than
16:10, e.g. 1.280 x 1.024 (5:4), are distorted by the monitor.
If the LCD is linked digitally with the graphics card, the
interpolation behaviour can usually be modified via the graphics card
driver: full screen 1:1 and justified. The graphics card does not
convert the entire image however, but instead sets corresponding
margin areas for the images which are then displayed and justified in
the LCD full screen interpolation. In this process, the LCD takes over
the actual interpolation work.
We rate the interpolated image quality of the ViewSonic monitor as
very good. Loss of detail or definition is at a very low level