What is best C# or C++ for making a game engine. I currently am a .NET C# developer and really want to use C#. Although I know C++ does support memory management and that is why a lot of big companies go for it. That being said C# is quicker in the development process and extremely familiar to me. Before anyone suggests it, yes I've used unity. I like it but want to go the long and hard extra stretch to own 100% of my own built game.
What do I lose by not going to C++? and what kind of libraries do I use, for graphics and stuff? Is that what DirectX is for? I'm trying to wrap my head around this and any help would be much appreciated.
I need some opinions
Perhaps I shouldn't presume to tell you what you need, but I think you'd be much better off receiving information you need to form your own opinion. Asking for opinionated answers (notice irony here) in my opinion isn't generally desirable here.
C# and C++ are both very powerful general purpose programming languages. Either language is 100% capable of creating full fledged high performing games. With that said, there are some (mostly) objective differences one can point out that may effect your decision.
Whether this is a pro or con for you is for you to decide. Some people want to save themselves work and have to spend little time taking care of memory. Obviously C# shines in this regard. C++ can have elegant and easy memory management if you know how to properly use smart pointers of course, but that's still more effort than garbage collection. If you're very concerned with having tight control over resources, then C++ might be more your thing.
When you want to write software without reinventing wheels (and you should) a language's libraries can be just as important as the language itself. This isn't an obvious pro for either language, as both have lots of libraries supporting games. If you have to pick a winner though, I'd say it's probably C++. The language has essentially been the vernacular of game programmers for years now, and has a lot of maturity in this domain. C++ can directly leverage APIs as low level as OpenGL and as high as Ogre3D. There's no guarentee that your game will actually benefit from a C++ library over a C# library though. It depends on your use case.
Continuing on the theme of libraries, this could be a pro for C#. C and C++ are two languages that have an enormous amount of libraries available. If you only count their standard libs though, then things change. Some people don't mind, or even like this. One may also want a more expansive standard set of functionality however. C++ doesn't have a small or incapable standard lib by any means, but C#'s is definitely more feature rich.
Unless you're going to use Mono, C# is not portable. Mono is a great option, but it does have cons (that you'll have to research yourself). C++ can't tow a line like "Build once, run anywhere", but it does all the same offer damn good portability if that's what you're going for. With an OpenGL renderer (or some higher level wrapper API like SDL/SFML) you can build for pretty much any desktop environment. If you're only worried about making games for Microsoft platforms though, then this point is probably mute.
This just like garbage collection is just a factor to consider. It'll be up to you to decide if it's right for your use or not. VM's sometimes have a stigma among game programmers it seems because of supposed performance issues. It's true, if C++ is used intelligently, it will probably be a better performing game. C#'s performance isn't anything to laugh at however. A lot of games that are written today can perform fine with a C# implementation. Is using C++ really an advantage if it means 450 FPS vs 400 FPS? Sure, there's a measurable difference, but it doesn't mean much to anyone playing your game, even if they have a 144hz monitor. Memory overhead is in a similar boat. Usually C++ isn't actually a necessity until you start getting into seriously heavyweight games.
Last but not least, consider the fact that you have tools you know, and tools you don't know. You already know C#, the time you have to invest learning is probably going to be much less if you choose to pass up on C++. C++ simply has additional concepts and responsibilities compared to languages like C# and Java. Some of these things you can choose to ignore. C++ won't hold you at gunpoint and force you to use multi-inheritance, and hey, that's probably easy to pass up on. Will you pass up on destructors though? Those are pretty important. What about the STL in general? Passing up on that is probably not a great idea, no best you learn STL if you're going to use C++. If you think this is worthwhile doing, then by all means go ahead. Again though, it's just something to weigh in.