I have one because they suit the British Army load out, when I bought it I was a very firm Sig P226 fan - because their ergonomics are amazing, all the features you'd want are all within reach of your thumb without you needing to shift your grip.
However, I was sold on the Glock almost immediately because of more or less one thing.
The grip angle.
Before handling a Glock this was never something I'd given any thought to, but holding one made me realise it's quite an important feature.
The Glock has a pretty darn steeply angled pistol grip, traditionally pistols are a lot more upright.
My hand just suits the Glock angle a lot better, with Sigs and M1911s I find myself pointing the muzzle down a little because my hand and wrist wants to relax a little.
The Glock is just natural point and shoot. Suits me perfectly.
Moving on from that though, they're so simplistic. Function over form, keep it simple stupid etc.
That's the Glock mentality I think.
There's no safety, decocker, trigger's single action only. Makes the mechanism a lot simpler, fewer parts means fewer things to go wrong, easier to fix when they do, ease of use and popularity make parts easy to find.
They're just great lol, I love the look too, personally.
For all the people saying the grip is small, have you tried the larger back straps on the Gen4?