@3ddreamer: What was your C++ friend creating for a decade.
He was creating a simulator ( Non-disclosure Agreement with me in effect here) with easier libraries and fewer of them than you want to juggle (for you the next 10-20 years) working long hours per day. His total lines of coding is less than those for your goals and he is a great coder with decades of experience, a real pro in C++. He has contracts currently with military and corporate giants, so this type of developer is the standard by which people will judge you - fair or not - if you attempt to accomplish huge game projects. The C# developer is a team leader and another international connected expert, but in an unrelated field of simulation software.
These guys got amused when posed with dreams like mine which I had of grandiose goals not far removed from yours. Years later I really respect these guys example which was a gentle kind of tough love on the realities in the business. Maybe they get so amused at newbies because they too had over ambitious ones several decades ago.
I didn't even mention the Java simulation developer (famous in some segments of the market), an acquaintance, who found himself years delayed even with a team in working on a simulation which is less than your goals. Subsequent updates and also finishing his next simulator saw years of unexpected postponement on release, about 5 years delay for the team in the last case. His next project, he finally learned his lesson and completed a lesser development size simulator which caused him to regain much of the damage to his reputation.
Keep in mind that all three of these professional developers which I know had huge budgets toward their team and still took years to make software which was smaller than your objectives.