For making the gameplay videos, there are a lot of free as well as paid screen capture softwares which can be used to capture the full screen via openGL and DirectX codecs.
The following is the best freeware gameplay screen capture software:
D3DGear: From my personal experience, I recommend you to use this software for capturing your gameplays. D3DGear does not causes much FPS (Frame Rates per Second) loss while playing the games, thus, making a good balance between the smooth gaming and swift video capture. There are several codecs which come with this incredible software like "fast MPEG-4 version 2 codec", "fast motion JPEG codec", "Huffyuv Lossless codec", "Windows media 9 codec", "AMD hardware H.264 codec", "Intel hardware H.264 codec". Now, if you have a powerful system with at least 4 GB RAM and a core i3 or AMD FX 6300 processor, then you should choose either fast MPEG-4 version 2 codec or Windows media 9 codec. With these codecs, software will unleash the power of your PC's cores thus making a balance between smooth gameplay and good video recording. But in case if you have a Dual core CPU then you can go for either fast motion JPEG codec or Huffyuv lossless codec. Huffyuv lossless codec uses the resources from your hard disk and thus the smoothness of video recording will depend upon the speed of your system's hard disk. And if you have a good GPU from AMD like the ATI 7770 or ATI R7 250x or higher series, then you can choose AMD hardware H.264 codec as the optimal choice for recording your gameplays.
There are other software also like FRAPS, DxTory, Bandicam, Action, etc. But I don't recommend using any of them. D3DGear is far more better than all of them and there is no competition for this wonderful screen capture software.