The premiere tournament event in pool is the US Open 9 Ball promoted by Matchroom. The fact that this is still technically the "world championship" doesn't mean anything to me.
At present, I disagree. I think the World 9-ball Championship, which had fifteen of the top 16 WPA ranked players in the field, remains the hardest event to win. The US Open 9-ball field remains filled with dead money, and the stars will tend to have little trouble in the early rounds.
In contrast, it is hard to qualify for the field at the World 9-ball Championship, Established stars like Zheng (Fargo over 820), Mario He (winner of the World Cup of Pool and a Eurotour event this year) and Nick Ekonomopoulos (former bronze medalist at the US Open 9-ball) all failed to get through the qualifiers. In the main event, Max Eberle, Hunter Lombardo, Niels Feijen, and Wang Can all failed to reach the last 64.
The US Open 9-ball is in the conversation for the de facto World Championship, and so is the China Open, which draws far more of the stars of Asian pool than the US Open 9-ball. Winning any of the US Open 9-ball, the China Open, or the WPA World 9-ball Championship is a tall order indeed.
The new Matchroom version of the US Open 9-ball is, without question, the best produced and staged pool event in the world, and it may yet evolve into the World Championship in the coming years, but to place it above the WPA World 9-ball Championship or the China Open is premature.
Like you, however, I'm excited about how they've stepped up their game at the US Open and with Matchroom at the helm, the future of the event looks bright.