We are a small company with only 2 programmers. We currently make small 2D and 3D games for desktop and mobile using Adobe Flash/Air. We want to stop using that framework and start learning and developing on C++ because there are much more and better libraries and frameworks available on C++.
I'm not sure about the libraries to use for rendering. I know that Ogre3D is a great rendering engine for 3D content but sometimes we need to make 2D games or "2.5D" games, sometimes with video playback, and all that need to be mixed with 3D scenes.
I know there are 2D frameworks like cocos2D-x and smfl that works with OpenGL (I don't know much about OpenGL) and can do all the 2D things I need, but can those frameworks be combined with Ogre3D? And can it be done without the need of knowing how all the Ogre3D internal stuff or OpenGL works?
If Ogre3D can be combined with any 2D engine, what do I need to learn to merge the frameworks?
Given that you have been using flash, I am guessing you are not porting old C++ code.
Also, since you don't want to know about how the internals of the framework you're using or how OpenGL actually works, you don't need a low level language like C++.
An abundance of open source libraries is not a very good reason to program your game in C++ either.
Unity3D has a free basic license, and provides everything you need out of the box.
For now, you can use planes with textures to do your 2D work, but Unity will also be coming out with a set of Native 2D Tools in the near future. Also, a new GUI system is being created.
For any C++ library you think you may need, there is probably something already built into unity that does what you want. If there isn't, there is probably a .NET port that you can use. And if all else fails, you can write a C interface for any library you need, and use it as a plugin in Unity.
One big problem with Unity though, is that you need Unity Pro to use plugins. Unity licenses are per-platform, So if you decide to use plugins, and release your game for multiple platforms, you could end up paying a lot of money in licensing fees.
Finally, it's not just an application framework you'll need. You'll also need a level editor. Building a 3D level editor is not a trivial task, and given that your team consists of only two people, this fact alone should be enough to seriously consider using Unity.
So unless you are porting old code, need low level access to hardware, or have specific needs for native code, my advice is don't use C++, just use Unity.