According to the official rankings of myself, the best teams of 2020 are Vitality, Astralis and NaVi

I've used the consensus ranking method from this paper to rank the teams according to their success in events that are deemed either S-tier or A-tier by Liquipedia.

Here are the results: https://i.imgur.com/WgppnBW.png

For accessibility reasons here is the top 10 in text:

1. Vitality

2. Astralis

3. Natus Vincere

4. .....