The best replacement for gtk is qt.

The best alternatives to gtk are rated as following:

Your alternative for gtk is not listed? Suggest!

Speaking about gtk, one probably shouldn't forget about opengl.

Other search terms related to gtk and their ratings are:

You have in mind a companion for gtk and it is not yet here? Propose!

Scale is based on the average worldwide traffic of gtk in all years. Click on graph for more.

gtk

wxwidgets