I don't know which is considered good, but I can tell you what my CAG's like.
My male CAG likes Psittacus pellets, and my female will only eat Nutri Bird P15 Tropical.
There is no specific bird food specially made for African Greys to my knowledge. There are many brands of pelleted food on the market that are good for all birds. Check the ingredients and decide for yourself which one you think is best.
From little to big - currently 6 Linnies; 2 Budgies; 1 BHP; 2 CAGs; 2 Zons; 1 GWM. Formerly in the flock: 1 LSC2 [fostered/rehomed] RIP: 1 budgie 1 WCP & 1 sweet Pan Am
Actually, there are foods made specifically for Greys. My neighbor just gave me a bag of Pretty Bird Species Specific for Greys & Conures (don't know why those 2 are even alike, but I think it might be because it is higher in calcium).
But to answer the original question - I mostly feed the Harrison's High Potency Coarse Pellets to all our birds, along with a lot of fresh veg. And other things (nuts, seeds & fruit) for treats.
harrisons description of high potency course reads Year-round formula for all medium to large parrots, especially African greys, cockatoos, large conures, eclectus, macaws and pionus. Other species may be switched to Adult Lifetime Formula after a 6 month conversion period....