Best is a relative term. If money is no object, then a Goretex or similar suit, with gaiters or booties and waterproof gloves is probably the best choice. Expect to pay several hundred dollars for a set up like that.
I have a Kirkland Signature two-piece nylon rainsuit that I bought at Costco for 29.99. It works great for me, but although I ride in the rain many, many days during a typical year (such is life in the Pacific Northwest), I rarely ride in a downpour for more than an hour at a time. For me, expensive and extensive rain gear is a waste.