For me, rock has to have energy. I nominated Hotel California above - I find the Eagles to be completely lacking in energy. I just can't get excited about any of their stuff. A lot of music is situation dependent - your age, where you're hearing it, etc. Guns 'N Roses in your car is great. Guns 'N Roses in the midst of some "serious" listening - well, you have to be in the right mood. The Eagles - I've never found a situation that makes me go, "Oh yeah!". Not that anybody would consider him highly enough rated to qualify for overrated, but Jackson Browne was/is the same way - geez, that's a tired sound.
Great Thread.