If you really dont want to play the first 2 installments (you should, seeing as the "Collection" goes for fairly cheap now-a-days) you can search for "God of War Cutscenes" on youtube and watch all of the cinematic events from the from them. It will at least get you up to speed on the story (given you played the games in numbered order) --- -=> este914 <=-
All you need to know about the first game is that Kratos was in love with a man named Ares. The love was unrequited which caused a lot of conflicts and awkward situations (as I'm sure you can imagine). Kratos slowly started to lose his mental faculties and descended into madness. The psychosis resulted in him going on murderous killing sprees in games 2 and 3. The games are basically like Shakespeare's Winter's Tale, except with many more pissed off people and much more vicious killing.
Deo: >GOW Gears summary? Sure. Humans move to an alien world with humanoids underground. Circumstances lead to them fighting for the right to survive and dominate the world. Humans are losing most of the time only to pull out the big win. The end.