Doug Bradley was the only reason I sat through ALL 8 of those movies. As said, 1 & 2 are almost factually awesome, but everything after that took a turn for the stupid. Sure, there were higher points (I thought Bloodlines was alright), but it also had some really, REALLY low points (Any mention of "Hellworld" inspires a vomiting reflex on my part).
And yet, Doug Bradley's role as Pinhead did not waver or degenerate once. Even as Pinhead's character began to degrade, Bradley kept up with it perfectly, and redeemed each movie more than a little.
I think this is kind of commonplace for some horror franchises. The "Saw" movies have pretty much become gore porn, but Tobin Bell's performance remained steadfast in it's awesomeness.
Likewise, as a big Nightmare on Elm Street fan, I can safely say that the series would've been truly lost without Robert Englund's stellar portrayal of Freddy Krueger. I don't care how stupid the films got, Englund made them incredibly entertaining. In fact, I'll retain that Krueger has to be one of the most fun to watch villains in cinematic history. He's not a particularly deep villain, but it fulfills the desire to know "Just what would happen if you gave a psychotic killer control over a universe that's limited only by his imagination?" It's the type of idea that fuels my deluded notion that Freddy's descent into silliness is more of a character development, more of him slowly coming to realize that he can literally do anything he wants in the dream world with no consequences, as opposed to crappy writers.