I'm using the following 3 fonts to replace those defaults,
Kristen ITC for english characters or system fonts
Eunjin for korean characters
Hua Kang for chinese characters (you will need one that support both simplified and traditional chinese or you will need another font for the other variant)

1. Copy the system font to Windows\fonts folder, while the korean and chinese fonts will go to the Windows folder.

2. Using any Registry Editor, navigate to the following keys, replaces the contents with the appropriate information from your fonts. Grab the font name from the font viewer. Changes to be made are highlighted in bold. Create a new value with the name of the new system font and value of those chinese and korean fonts.

Courier New = \windows\huakang.ttf,Hua Kang;\windows\eunjin.ttf,Eunjin
Tahoma = \windows\huakang.ttf,Hua Kang;\windows\eunjin.ttf,Eunjin
Kristen ITC = \windows\huakang.ttf,Hua Kang;\windows\eunjin.ttf,Eunjin

3. This value registers the system font, so change the value to the one you want to replace with.

Nm = Kristen ITC

4. Now create a new key under GDI with the name FontAlias, and create a new value with the old value from Nm (previous step) and the name of the new system font.

Tahoma = Kristen ITC

5. save all settings and restart the device =)

finally get rid of the monotonous fonts!

(P.S. some areas like the Today screen still remains in the original font, one solution is to place the desired system font in windows directory. But the side effect is having the sms view mode messing up)

Here's the link to the huakang.ttf, tis version is rather large as it supports both simplified and traditional chinese, and japanese