Depends.
For starters what is your definition of "best"- cheapest, most accurate, easiest to get, supported by your phone, what functionality do you need...?
Then there is just our individual body - some people have no issues with Libre (it's the most common), many people who try a Dexcom say that is less fault prone (but I found it less accurate and had a 50% failure rate).
Finally, it is important to remember that all CGMs are designed to be most accurate at "normal" BG levels and, like finger prick meters, need only be within 15% of the "real" BG. If your levels are in double figures or your finger prick meter you are comparing it with is 15% out in the opposite direction. no CGM will appear accurate when compared with finger pricks.