John Mueller of Google had to say in a Google Webmaster Help thread that adding a YouTube video to your page will not make the page high quality by itself. Videos from YouTube on your pages won’t give you a ranking boost or show Google that the page is higher quality.
John wrote “A YouTube video alone doesn’t make a page high-quality :), but you can certainly use videos as a way of providing more information to users.”
We did report that John said in the past that these videos can slow your page speed, which technically may have a negative impact on some ranking signals. But honestly, YouTube embeds are fast and won’t slow you too much where it impacts your rankings in a negative way.
But at the same time, it won’t directly give you a ranking boost.
Forum discussion at Google Webmaster Help.