Update: This solution doesn't work anymore on Mountain Lion. If you have to support 4.x I suggest you don't upgrade to ML and stick to Lion and Xcode 4.3.3. But, I'm guessing it's too late now since you're already here and reading this.
Xcode 4.3.3 doesn't work in Mountain Lion.
If you want the 4.x simulator back into Xcode 4.4 here's what you have to do:
- Download Xcode 3.2.6 and iOS SDK 4.3 from https://developer.apple.com/downloads/ (you must be an Apple Developer to have access to that area)
- Mount the .dmg file
- Inside the disk there should be an invisible "Packages" folder. To open it use shift + cmd + G (Go To Folder) and type "/Volumes/Xcode and iOS SDK/Packages/"
- Install iPhoneSimulatorSDK4_x.pkg in a temporary folder
- Once installed go to your temp folder and you'll find a iPhoneSimulator4.x.sdk file
- Open a new Finder window and navigate to "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform" (you can do this with the same command as above, shift + cmd + G)
- Drag the iPhoneSimulator4.x.sdk from your temp folder to the SDKs folder of the Xcode package.
- Restart Xcode and delete your temp folder