Here's a software that will allow you to change the screen size for any game made for any Nokia series 60 mobile (preferably Series 60 V3). Just install the .Net framework and then setup this software.
Run the exe file.
Select the base screen size (in the first drop down list)
Select the target screen size (in the second drop down list)
Click on the 'Select & Resize' button.
A select file dialogue box opens...select the base jar file and click 'Ok' and voila... u have your game in the required screen size.

Pros:
Works for most games.
The playability is not affected.
Cons:
If the games use the device font for the text then the font size becomes too large.
The images in the enlarged games are not very crisp.