> I've tried all the open source MSPaint alternatives, and none of them even come close to being as good as MSPaint.

KDE's kolourpaint is basically a clone with more features: http://kolourpaint.sourceforge.net/screenshots.html

Pinta has this layer idea more prominent, but it can still be used as simple as you want: http://pinta-project.com/

mtpaint has a lot more features than ms paint. The gui is unintuitive, but if you get used to it I'm sure it's just as easy: http://mtpaint.sourceforge.net/