Have you ever shot before? Everybody's body, hand, eye, etc is different. The Glock works great for some people, and isn't so comfortable for others.
Glock makes at least a full size(17), compact(19) and subcompact (can't remember the #) in 9mm. They all feel very different in hand. The 17 is very uncomfortable for me whereas the 19 fits my hand better. Glock has a pretty unique feel to it and most either love it or hate it.
For self defense your primary concern is reliability. Most of the major manufacturers of pistols(HK, SIG, Glock, Springfield, etc) have this element down. Similarly, most pistols made by these manufacturers are probably more accurate than you are. Get out and shoot a bunch and see what you like. Pistols aren't cheap, and it's worth a little extra time to find the right one if you are only buying one.
Although I don't personally own one, Springfield's XD line may be worth considering if the Glocks don't fit you right. They are priced well and shoot well, much like the Glocks. That said, Glock makes a great pistol and out of their 9mm's, I strongly prefer the 19 from an ergonomic standpoint. Additionally, it's nicely sized in that it is large enough to be comfortable but small enough to carry/conceal comfortably, if that matters to you.