I would agree with you if we already didn't have F-18, F-14, F-16, F-4, F-5, JF-17, AV-8, Mirage 2000, AJS-37, Mig-21. As I see it Su-27 and Mig-29 are the last ones that actually will give you some profit. Misunderstand me correctly, I'm not trying to argue, its just that your argument do not hold since there are no more aircraft that can be made that would be more popular then Su-27/Mig-29.
So do some money ED and start to develop Su-27/Mig-29, there is nothing else there that would sell as good as them.
My best wishes!!!