Underoath didn't used to suck. Their first couple CDs (something about depression, and something about crying), when they were actually black metal, were really good.
Now they're complete shit. Same with Norma Jean. They were good at one point, and now they make me want to kill myself. Which I guess is very metal in its own way...
Christian metal has simply devolved. Ironic.
EDIT:
Old Underoath
As for other bands, I saw
Extol and
The Agony Scene in high school, and they were both pretty good at the time. Based on the music video, though, I'm guessing Agony Scene has gone to shit.