If you want to develop your games in C/C++ then AmiDevCpp is an option:
http://amidevcpp.amiga-world.de/
If you don't have an OS4 Machine, developing for OS4 is very very difficult, because you can't debug your programs. You can better develop your games for OS3.x and try it in WinUAE. Developing and Debugging for AROS is even easier.
Yep I agree, developing software for a machine you can't test it on is almost pointless. I spent quite a lot of time developing ScummVM in C++ for classic Amiga's without a real machine so I had to use WinUAE for testing. I'd do what I thought was a really good build for 030 AGA machines but when people tried it on their Miggys it would be as slow as hell and flicker like a b*tch! In the end I gave up and brought and got a real A1200 again for testing my ports.
Of course WinUAE is better than nothing (I still use it for prototyping and as my 'virtual' ECS/RTG Amiga) but it's no good when you get to the optimization stage of development (esp important for Classic HW).
