Some solos where Petrucci doesn't shred are among his best, I agree, like Lines in the Sand. But he has a few of pretty great shred solos, like In the Name of God or The Enemy Inside (though I'm not sure if that qualifies as shred), and some of his slower solos aren't, at least to me, not emotion-filled, but just plainly... well, boring is exaggerated, but certainly not very good or interesting - Razor's Edge being the prime example.