Well, OGRE which is one of the most popular open source engine, has many toolkits. See the download page. There are enough toolkits for major applications. And, that page shows the ranking about popular applications at OGRE. That’s interesting!
The most popular application in OGRE is 3ds max. But, the toolkit for max is the first tool in OGRE. So the toolkit for max is downloaded at each time which new version is released. But, anybody agrees popularity of 3ds max.
We should pay attention to the rank of softimage XSI. XSI is the worst, because Blender registers two items. But, XIS is really excellent for game development. It has the best environment for plugins and programable shader, and it’s reasonable. Why is XSI minor? The article of Wikipedia (JA) says about the reason;
Because most 3d applications are high price, most uses don’t want to change their favorite application.
The dialog for shader pipeline at XSI is excellent. TDE is interesting environment. XSI should become more popular.