I see what you're saying—I guess I would rather risk getting one great movie and one bad movie (ie. Raimi's SM2 and SM3) than merely two mediocre to good films. I can swallow that failure if that is the cost of the gamble. Plus, often, failures make for just as compelling films as successes when they have a strong, sustained creative vision behind them—however misguided or poorly executed that vision may be. And I think there's value in that as well. I get more out of a "bad" Spiderman 3 than I do out of a dull, but competent, Amazing Spiderman.
As an aside, Life of Pi makes me so interested to see how Ang Lee would have handled Hulk with today's technology—I've always felt Hulk's biggest problem, critically and commercially, was that it was an ugly film that looked dated the day it came out.