That is a tough question.
The Sig P210 is highly regarded as one of the best and the most accurate.
The Browning HP is considered one of the best ever.
The CZ 75, especially the P-01 is a great 9mm.
The Sig P226 is a fantastic 9mm .
The Glock 9mm is widely regarded by some as the best defensive pistol ever made.
For me, the M&P 9C has all the best combination of all qualities that I think make it a great weapon. It is reliable, super accurate, great ergonomics, etc.....
I think as far as modern 9mms the Glock, P226, P-01, and the M&P (probably the XD 9mms too but my experience is very limited with them) are just too close to call and it will vary by shooter and by mission the pistol is intended for. The HP and the P210 are great 9mms but they are getting a little long in the tooth compared to more modern offerings. They may still out shoot the new ones though.