Games on a Flatscreen?

Should be no problem.  The flat screen monitor acts just like a regular monitor since it is driven by the same video card.

And whats about the "ghost pictures" ?

It's the same issue.  When the computer updates the image faster than the LCD elements can respond you get a blur and/or a ghosting effect.

Again, be sure you see on one action before buying it.  Be sure you buy the same make and model you see as they are not all created equally.

A Flatpanel is made for one specific resolution. (15'' = 1024x768; 18''=1280x1024). What about the "zooming" resolutions? Are they blured too or are the new panels better in zooming?
Thanks for your answers
 

The blurring is NOT due to resolution but rather to the speed at which the LCD can update itself.  Please don't confuse the issue.  The closest analogy to CRT displays is the persistence of the phosphor but you rarely see that as a problem these days.  If you've ever seen an old green screen vector display (like an old Tektronix 4014) you know that an image stays in place for several seconds after a new one is drawn.  On a 4041 display, this is a good thing.  On a fast changing game display, it's a nightmare.

You are correct, however, that an LCD is built for one specific mode although most will stretch or crop an image for the standard MSDOS boot mode display and the 640x480 VGA display mode for compatibility purposes.