I plat a lot of war strategy games like age of empires 3, command and conquer 2 [yes I still play this game from 2003], I upgraded from a 19" 4:3 to 24" widescreen.
The height of the screen is almost exactly the same on both, however the width is another 66% added and it makes a lot of difference.
Although I can't help but thing for strategy games where you need to see the battlefield a 4:3 would be better than a widescreen.