Kronk obviously has to be considered #1 Zhilei Zhang's gym is also really good. Kurt Li has trained Fanlong Meng, Zhilei Zhang and Can Xu, which is a very good collection for one small gym.
It depends what you are looking for. There are excellent teachers in gyms all over the country, people that you will never hear of. Most of the gyms that hit peaks of recognition do so because of the sparring available. Trust and believe that nobody goes to the Wild Card because of Freddie Roach. They go because of quality sparring and that has varied over the years; for a while it was the spot for 168 pound guys, and it was a long time place for 140. Ronnie Shields is hot now in Houston, with good sparring from 130- 160.
I can't recall what the name is but Klimas bought Robert Garcia's old gym and it became the center of a lot of training camps for his Eastern European crew--Lomachenko, Besputin, Usyk, etc. Garcia's new gym, which I believe is called RGBA (Robert Garcia Boxing Academy), is also prestigious. The Wild Card still gets a lot of guys coming through, though it's not as popular now. McGirt Boxing, Plex Boxing (I think that's where Ronnie Shields is), World Class Boxing Gym (Derrick James), wherever Andre Rozier makes his home, the Olympic Training Facility in Colorado Springs, and The House of Boxing has some pull because it's where Alvarez makes camp. There are good gyms sprinkled in California and Nevada, though.
There is also a RGBA gym in San Antonio, which is run by the father of Hector Tanajara Jr. San Antonio has a very solid amateur program and funnels those guys to Robert Garcia in Riverside.
