Well, so far, I've watched the pilot movie and the first eight episodes...my favorite quote would be the one from G'Kar, when he picked the ant up from the flower in 'Mind War' (I think).
I'd have to pop the DVD back in to get the exact quote, though.
Love that one too (love just about anything that came out of G'Kar's mouth really --- I know it was JMS, but Andreas delivered the lines with a gravity and a sincerity that few others can, or could).
To clear it up: G'Kar is talking to Catherine Sakai about the beings which dwell near Sigma 957 (which we now know are/were the First Ones). He asks her "What do you call these creatures?" She replies they are ants. "Ant," he says thoughtfully, and carefully and gently picks one up.
"There", he says, "I have just picked one up on the tip of my finger. If I now put it back down (he does), and another ant asks it "What was that?", how should it know what to answer?" (That may not be perfect: I'm ging from memory here).
Beautiful, beautiful writing, so simple and yet so deep it frequently made me want to cry.
Again, G'Kar: "If the symmetry were any more perfect, I believe one of us would break down in tears!"