I've never heard of TDK being described as a "feel-good movie" before. I thought it was dark and downbeat, and it ends on a much more depressing note than DKR does.
DKR is pretty depressing. If movie watchers paid attention they notice that the Batman didn't really change anything. The people didn't rise up against Bane and they never were really inspired by Batman. They are as apathetic as they were in Batman Begins except their city is in worse shape then before.
Rha al Ghul was right and it's probably why Bruce Wayne gave up and handed the reigns to Blake.