Beretta 92
Glock 17 or 19
HK USP or variant
Sig 226 or 228
It is purely a matter of opinion which of the above is better than any of the others, so I've presented them alphabetically.
Ergonomics:
Beretta and Sig are tied for best, then HK, last Glock
Reliability:
4 way tie, near'n I can tell.
parts availability:
Glock is best, the others are tied for distant dismal last.
Accuracy:
4 way tie, but the Glock has the ####tiest trigger going, so gets edged out.
field stripping:
Sig, Beretta, Glock, HK, in order of ease. Sig edges out beretta because of that f'n locking block.
Detail stripping:
Glock, then dismally far behind, a 3 way tie.
I value parts and detail strippability over ergonomics and trigger, si I like the glock. To coin a phrase, your mileage may vary.
On the radar for "best 9mm", it's important to mention the S&W M&P (heretofore referred to as '&&') and the Steyr MA1. Only time will tell, though.