Popularity doesn't necessarily mean more screen time is deserved. Glen is popular... why? I don't see it. He hasn't done much, action-wise, since the first season when he rescued Rick from the tank. And the Season 3 finale. But everyone had to do their thing in the finale, so it's not like he's particularly outstanding in that matter. Other than that, he's been just another guy on Hershel's farm. Daryl, that I can understand---the guy has excellent hunting skills, has a long-range silent weapon, and is likely extremely capable of surviving out on his own for a long period of time. As for Glen's popularity, I can't see it. Or, at least, not yet. Glen has a great skill for scavenging, and he should be seeing more action in the next season.
T-Dog, I don't know what's going on with him. He spoke more lines in the finale than he did for the entire second season, it seems. He has virtually nothing to do on that show but exist. It's a shame. He's able-bodied and NOT mentally broken, and yet Carol gets more screen time and lines than he does. It's very strange.
Also, Rick is the main character, so anyone directly interacting with him is going to get the most screen time (like Lori and Carl). So that just makes sense, seeing the interactions and dynamics between them. The Walking Dead is a zombie story, sure, but the real horror of it all is what previously rational, level-headed people are/can be reduced to when the s**t hits the fan.
