Wayland is kind of unique in that it is deliberately, intentionally impossible to run applications written for any other window system on top of it. All the others are pretty well cross-compatible - Win32 applications can run on X11 and vice-versa with an appropriate compatibility shim, both can run on OS X just fine too, and in theory OS X apps could probably run on other platforms if anyone cared to develop the code to do it, but none of them can run under Wayland. By design. The only reason XWayland works is because every Wayland compositor currently bypasses the limited Wayland APIs and implements a large chunk of X-specific code to enable it, and if they ever get tired of maintaining that say goodbye to compatibility with any existing pre-Wayland GUI applications regardless of original platform.