Not quite. Your phone's content will still be pretty sharp, and the vidoe will use all the pixels on the phone's panel.
That's not the case in VR. Not all the pixels on the panel are used to render the image, and the image will be a representation of the video at a much lower resolution since it's a projected canvas in 3D virtual space.
It will be more like watching a real video player stream (remember those?) or a low quality youtube stream than watching your HD phone.
If you've ever used one of those $100 ultra portable subHD projectors, you might have an idea of what ti woudl be like. IT looks cool for like 5 minutes, having that HD movie up on a big wall... and then you realize how low quality it is and you go back to watching it on your TV.