What is the best Glock?  To answer that question requires a followup question; how are you going to use your Glock?  I will answer this question in several applications, and then I will give the overall answer.

Law Enforcement
The most widely used Glock in Law Enforcement communities is the Glock 22.  This full sized 40 S&W is a great gun that bridges the gap between the high capacity 9mm’s and the old single stack 45’s.   The 22 allows you to have a high capacity gun that still puts out some serious energy.  The only downside is the increased recoil.

Competition
For competition shooters in IDPA many of the best shooters are using the Glock 34 9mm.  It comes with adjustable sights and a lighter trigger pull than standard Glocks.  The longer sight radius makes shooting easier, and felt recoil is almost none.

CCW
The person looking for the perfect Glock for CCW or for all around use should look no farther than the 19 9mm.  This gun gives you a high capacity gun that will still easily conceal.  That makes it perfect.  Unlike the subcompacts you can get a full grip on the gun and the sight radius is just long enough to make all the shots that you need.

Obviously there are a lot of models that weren’t mentioned, and that is the nice thing because there is truly a Glock available to suit your specific needs.  Having shot or owned almost all Glock models available, I can truly recommend them.  Remember, only buy a gun you can shoot fast and accurately.  That will determine the caliber, length etc.