What is defined as "Best"?
are you just looking for a cost-effective basic green? --> Jack3d Factory Green Surge, Primeval Day 2 Day
Do you want additional digestion support? (Enzymes, Probiotics, Prebiotic Fiber) --> Ghost Greens, Gaspari Greens
Are you looking for additional hydration support & Digestion support? --> BEAM Greens
Really too much of a black and white question as to what is best as that is too subjective from person to person, and what they look for in a greens product. All of the suggestions above are great products. It just comes down to personal preference.
If you listen to Doug Miller's podcast, he went hard a few weeks back about why his Green's product is the best in terms of composition and taste. Obvi he is biased, but, if I were going to try a green's id probably try his first.