I wouldn't call a counter strike that puts georgians back on their home territory an invasion.
Besides, the first strike was made by Georgia, WHILE the Olympic games were on, and they killed a hell lot of civilians in that, only then Russia came in to protect.
The Full picture looks like this : Georgia kills civilians in South Osetia while everyone else has a "seize fire", Russia sends 10k troops to South Osetia who make Georgians retreat back to Georgia. Georgian president offers truce, Russia refuses. USA, EU and other countries tend to think Russians are bad guys because it's blocking their oil pipe