I am a LEO and have been fortunate to be assigned to a unit that shoots a lot over the last many years. I've been issued a Glock this whole time and never really got too exited about it...you know "plastic pistol" and all.
Personally, I've owned and shot Sigs (P229 and P226--my personal favorite), Beretta 92, HK, Walther, Smith autos, Springfield XDs, and a few other Duty type weapons.
In the end, if I had to grab a handgun and run into trouble in progress, I'd grab a Glock. Let me tell you why:
The trigger system on a Glock is easiest to shoot quickly and effectively. You can teach anyone to double tap well (accurately) with a Glock. The trigger reset on a Glock is safe yet effective. (I guess if you're willing to train a cocked and locked system then a 1911 would be a top trigger.) When I see people list Sigs/Beretta I have to wonder...because much speed is lost in the DA/SA first pull...and when you try to shoot the long trigger pull quickly accuracy goes down.
Glocks are supremely reliable. I've stood on the line at the range with 40 other guys issued glocks shooting thousands of rounds over the years and I'm still amazed at the level of reliability. I have two issued Glocks that have never misfired or failed to fire after many many long days at the range.
Glocks are tough and durable. Snow, rain, mud, climbing holstered over brick walls, crawling holstered through the brush, bla bla bla, and they still perform well. I've seen Glocks abused that still perform reliably. (Caveat--the people I shoot with clean and lube their weapons after every shoot/training day.)
Glocks are light weight. Carrying a handgun daily brings one to appreciate weight. (I know lots of gun enthusiast cops who have custom 1911s in their safes after they got tired of the weight on their belts all day every day and elected to carry something lighter.) A Springfield Operator (a pleasure to shoot and own) is a heavy beast (yeah, it's in my safe.)
Glocks are accurate. I've never seen a Glock that didn't shoot to point of aim after proper adjustment. Glocks will shoot consistently small groups...right up there with the best handguns.
Glocks are high capacity...typically.
Glocks handle/absorb recoil well and they naturally point well. The ergos, while very bland, are utilitarian and very functional. (CZ75s have great grip ergos.)
Glocks are easy to maintain. Glock barrels and slides don't foul easily and clean up easily. The teflon coating...or whatever it's called, keeps the pistol clean a long time. The pistol is easy to take down.
Glock magazines are bomb proof. Doing drills on a range with asphalt can be really hard on magazines. Drop a fully loaded mag on the tarmac over and over again and you'll see failures. I had to give up my Springfield XDs because the mags couldn't take a regular training day without damage. Damage=failure to feed. Good magazines are EVERYTHING in a duty weapon.
Glocks are simple to deploy...they have no external safety. In my experience, handguns with safeties are trouble under stress (Unless you train and train regularly). I can't tell you how many times I've seen people draw and pull the trigger on a "safe" weapon when surprised by a threat in training scenarios.
There are so many other pistols that are so much sexier! I love my Sigs, CZs are nice, and I have an HK USP that I adore. But, in the end, I'd grab a vanilla, tupperware, boring, Glock 17 if I was going into harms way.