Xcode is a really hard one to replace because at the end of the day you pretty much have to use it at least a little bit so some developers will probably choose to use it just so they don't have to use two editors. I'm not aware of many/any other languages/platforms that are that locked down (at least in mainstream programming)

Windows and game consoles.

Yes, there are tons of stuff you can do on Windows without Visual Studio, but then you aren't doing all the scenarios a Windows developer might care about.

There is also that little bit only available in a mix of Windows SDK and VS plugins.