I always just leave mine alone. Because just because it's not doing well now, doesn't mean in time it won't hit a sweet spot in SEO.
Prime Example: One of my videos that I had uploaded in the middle of January topped at 200 views in the end of February. I thought that was the end of that and it'd probably stay there. A month and a half later? It hit a good spot and garnered a bunch of views basically over night and went to over 1K views. Now a month later it's about to hit 2K. Granted it's not an astronomical number, but it's still garnering views almost 5 months later.
Now when you type in the Search Term "F*** Girl" or "F***Girl" into YouTube (which is a fairly popular word in this day and age lol) My "How to be a F***Girl" Video is one of the First videos to pop up.
NEVER delete videos just because they aren't doing well. People may come to your channel 2, 3, 4 months down the line and want to watch that specific video. Which they obviously can't do if you delete it, lol.