History of Violence and Road to Perdition were seen without knowledge that they were inspired by graphic novels (aka comic books.) The result was befuddlement as to why they were so highly praised.
Ignoring the gorgeous cinematography by Conrad L. Hall, the tempered and beautiful score by Thomas Newman, the wonderfully crafted sound work by Scott Hecker (and the rest of the sound department), and a good acting performance from the late Paul Newman (of which he was nominated for an Academy Award)...yeah, I suppose you could wonder why Road to Perdition was highly praised.
A History of Violence is more uneven, for sure, but even with the trappings of a mainstream film, it manages to keep enough of the Cronenberg aesthetic that it's easy enough to understand the praise.
But if you'd like to imagine they were praised because they were sourced from comic books/graphic novels (I neither care enough for the genre nor know enough about it to distinguish the two)...well, go for it.