An interesting point. There is no doubt that Russian Knights and Swifts aerobatic teams are ONE OF the best in the world. Certainly top 5-6. In terms of solos they ARE the best in the world due to maneuvering characteristics of MiG-29s (Swifts) and SU-30 SMs (Russian Knights). Now Russian Knights transitioned to a combat aircraft which generally defies aerodynamics--SU-35C.
It is a massive upgrade and one can only imagine what those planes will be doing at the air shows. They will be stealing it. Go to around 6:20 (if you want to skip other mind-boggling maneuvers) in this video and prepare to pick your jaw from the floor.
But having said all that, I, in full consciousness, can not say that Russian Knights are ultimately the best. One of the best? Absolutely! Probably even top-2. But I have to admit that as a team (formation) flying Blue Angels deliver. Their, namely team, flying is so amazing, that it is impossible to deny. It is insanely clean and tight.
Here are Knights in Lima, Peru.
Basically, top 5-7 teams in terms of formation flying are very closely matched: Thunderbirds, Swifts, Patroille de France, Frecce Tricolore etc. Plus, I hate all those fanboys' ratings of "top-10 best whatever", but in terms of formation flying the Blue Angels are probably the top team in the world. For now. And even this position is hotly contested by the number of superb aerobatic teams all around the globe and that is why I prefer a more neutral definition--one of the best in the world, because there is more than one. Let them all just give us all joy doing what they do best--beautiful flying.