They don't suspend our disbelief, they overwhelm it. Much of the appeal of blockbusters is ascribed to our thirst for violence or the desire to shut our brains off. And while that's not entirely wrong, it's not the whole picture. But it is why the spectacle is relegated to the realm of the guilty pleasure, the kind you don't defend when your aesthete friends are flogging Abbas Kiarostami. And we're the better for it.
People like to call blockbusters insulting to the intelligence.
An easily insulted intelligence is a feeble one. Only good can follow. Spectacle or no spectacle, a lot of these movies blow, as anyone who saw Independence Day or, I presume, Battlefield Earth can attest. By delivering graphic evidence of the literally impossible, of hugeness beyond conception, they expand the parameters of our capacity for wonder. You don't believe it, you see it.