'the hulk'

The Hulk's origin was only one of the things I hated about the movie.

In all fairness to Ang Lee, he was trying (to an extent) to be faithful to the Hulk's origins and powers as developed over about 40 years of continuity.

Stan Lee and Jack Kirby set out the basic template of the Hulk's origin, with the gamma bomb that exploded while Bruce Banner was saving Rick Jones. Bill Mantlo later developed that in the mid-1980s by making Bruce Banner's father into a research physicist with a streak of paranoia who believed that his work with radiation had caused mutations that his son inherited. If memory serves, he also added the touch that the elder Banner had murdered his wife.

Peter David, during his remarkable run on the series in the 1990s, put forward the explanation that the Hulk gets stronger the madder he gets because his anger actually is leading to heightened cellular reproduction -- more muscle tissue, plus healing so fast that it appears the Hulk is invulnerable. (I think he stole that idea from the Hulk TV show.)

The nanobots were just a stupid addition. They really should have stuck with the basic origin involving Rick Jones and the gamma bomb. Predictable, but there's a certain strength in sticking to the essentials. You don't need to follow it in every detail, but you shouldn't chuck out the whole thing just because it's dated.