I believe it is far simpler to Import all, then use Lightroom's full-screen view and X flagging to delete the unwanted.
Import dialog shows the small camera thumbnails.
The Previews created by LR after import can be 1:1 previews with detail.
The previews visible on the Import grid before importing are what the camera has embedded in the image or video, so LR may not have much control over what is being shown.
You’re not supposed to be judging if the pictures are good before importing them. That is something to do afterwards.
If you want to upload the JPG you show there, somewhere like http://www.dropbox.com, and post a public download or share link, here, then others can download it and see if they have the same issue.
There is a website: http://regex.info//exif.cgi <http://regex.info/exif.cgi> that you can upload your photo to, to see how many different embedded previews there are in the JPG. It is possible that there are multiple resolutions and LR isn’t choosing the larger one.
Thanks, from now on I will import all of my photos. The only reason I still want to know is because sometimes I take time lapses with thousands of photos and just pick out some of the them. I uploaded the photo to the provided website, and there is more than one embedded preview. Do you know if there is any way to get Lightroom to show the larger resolution?
If you want to show more than one photo at a time then the embedded thumbnail from your camera is the only option and that will be, as you've already seen, poor if enlarged as you've shown. For single shots the preview is (usually) much higher quality.