Rick, Glenn, Daryl and Hershel are all likable characters. Dale and T-Dog were as well.
Shane was a good character, in a development sense not a morality sense. I don't get the Rick and Glenn hate, nor the cardboard cut out point of view.
I also like Michonne. A lot. Merle and the Governor are interesting characters who make the show better. Tyreese and Morgan too, I'm hoping they both become regulars in season 4. I didn't think any of the comic characters introduced after the prison arc lived up to the ones that came before.
In the show the Governor has killed the chopper pilot, killed all the national guard soldiers, ordered his men to kill Michonne, tortured Glenn and Maggie and attacked the prison, killing Axel pretty much because he just doesn't like them. He is insane with power, but the show has pulled him back to the point where it's understandable for the townspeople to trust him, instead of in the comics where he seemed to just be an insane mass murderer and the townspeople were either too scared of him or idiots.