Asking advice on critiquing something good

I finished Smokin' Seventeen last night and I finally got my copy of A Dance With Dragons by George R.R. Martin. Oh, I've been waiting years for this. In terms of fantasy, grit, world building, characterization, and breaking all the rules, Martin is my idol.

I have to set the book aside for the moment and focus on critiquing a few short stories for my writer's group. We're meeting this Saturday. Sometimes it's hard to critique stories. I'll find a few technical errors, but the story is sound. I offer my compliments. Then that's it. I feel like I'm not doing my job as a critique partner. Yet I don't know what else to say! Any advice?

I got one of my short zombie stories short listed yesterday. It's a medieval zombie story from a zombie's point of view. It would be cool to get published.