There could be several reasons why the uploaded quality may not be as high as the original video recording.
1) When videos are first submitted to the website, and you receive the link that you can go view it, you may only see a 480p version of that video. The reason is that it takes more time to process and finish uploading the 720 and 1080 versions. You should only have to wait a few minutes (depending on the length of the video) to see the higher resolutions.
2) You will want to ensure that 'Optimize videos for upload and share' is not enabled in the Preferences as that reduces the bit rate and video size up to 720p at 30fps. This option is mainly for those who wish to upload videos faster at the expense of reduced quality, or have limited bandwidth to upload videos. You can find this option in the Preferences under 'Advanced'
3) As of July 2016, we made a change in how we generate video resolutions in two phases. At the time of upload, you should be able to see the 360, 480, 720, and 1080 resolutions available as viewing options. 720H and 1080H (which represent higher framerate videos) are not generated immediately.
After 50 unique views are reached, the video becomes placed into a queue to gain the higher frame-rate versions. Keep in mind that they must be unique views (so refreshing the page won't work), and the number of 'Likes' is not a factor.