Downsizing the resolution to 50%, but not the quality

Hi folks,

I have tried many converters and compared each of the results of the converted videos.
For me the mp4 with h.264 seems ok for now.

The original resolution is 1280x720 (mp4, 25fps), and i would like shrink it to 640x360. The size of the file is not important for now, only the quality. As I am going to cut and edit them in the near future to the latter size.

So, whenever I do the conversion, whatever tools or settings I use, even higher bitrates, I find out that in the end I never achieve the quality the same as the following:

When I watch the original video file and just resize the window of the player to 50%, I realize still how clear, sharp and vivid colourful it is.

Like that I would like convert the video to a similar result. I think if that is possible to see such a quality while watching, then it should be also somehow possible to have it converted and resulted the same way, shouldnt it? Or what do I do wrong or do I forget somethings in the settings? any suggestions? Or is that not possible?

I hope somone can help me out of this. im really bit frustrated.
Any help or advice is appreciated

Cheers
silencer