I actually did like the Ghost Rider issue because it seemed to validate the Hulk's mission. The Spirit of Vengeance, according to Dr Strange, has infinite power to carry out his mission... but as a spirit of vengeance, he couldn't interfere with said mission because the Illuminati weren't innocent.

Greg Pak: Way back in Strange Tales #156 and #157, Dr. Strange summoned an extradimensional demon named Zom in order to battle Umar, Mistress of the Dark Dimension. Crazy hijinks ensued, including Umar hightailing it back to the Dark Dimension, Zom announcing that all of mankind shall fall before him, Strange defeating Zom by the handy expedient of severing his topknot, and the Living Tribunal showing up to condemn the Earth to destruction because by severing Zom's aforementioned topknot, Strange had "awakened a sense of evil which had slumbered for ages in the bosom of the mystics of mankind." Good times!

NRAMA: Undoubtedly. But how in the world did you ever find him for use in this storyline? Was this something as uber geeky as you always wanted to have Strange sip from that bottle again, someday, or, in the early drafts you knew that you needed Strange to be able to go toe-to-toe with the Hulk, and Zom was found later?
Mark Paniccia: Greg called me up and tells me he's discovered this really cool element to add to the Strange scene..."ZOM!" He starts explaining the spike/mace ball hands and that Strange will have a flaming head and I'm thinking of how cool this visual is gonna be. Plus, it tied into Doc's broken hands. It was perfect. When I saw what Johnny designed, I just smiled. This 20 foot tall amalgamation of Doctor Strange and the devil himself looked like he could give Hulk a serious run for his money.

GP: We always knew that after trying and failing to end “World War Hulk" by reaching his friend Bruce Banner, Strange would be pushed over the edge. Zom was the perfect continuity-based element from Strange's past to draw upon. As Mark says, it made sense down to some of the smallest details -- Strange's hands had just been crushed, but his Zomified state would give him maces for hands.

I think the Hulk's plan is to make them go through what he went through. Next up would be losing someone they love, and that'll probably be when the Sentry shows up.

They explain the demonic Doctor Strange thing on Newsarama (though, yes, they shouldn't really have to) thusly:

And the business with making the Illuminati beat each other up? THAT'S the Hulk's big revenge scheme? Lame. Wouldn't he want to knock them into dog food himself?

Yeah. Waaaaay too obscure a reference.

I think they're clearly setting the Sentry up to fail. He's told by Stark to "play God". Look what happened to the Illuminati when they decided to play God with the Hulk.

Just sayin'.

The difference between The Sentry and Superman (or Gladiator, for that matter) is that the Sentry constantly has the fear of doing too much, using too much power, and unleashing The Void if he does so. It's a twist, in a way, on the "With great power must come great responsiblity" in that he has to choose carefully how and when he uses his power.