It would be exceedingly difficult to claim that a movie didn't portray the Hulk's strength accurately, for one simple reason:
The madder he gets, the stronger he gets. 
Thus, any time the Hulk appears to be "weaker than he should be" could be argued away as merely a reflection of his lack of sufficient anger at the given moment… Or, in general, a lack of adrenaline, which is not always induced by anger (there's a scene in The Incredible Hulk which covers alternate potential means of transformation, but those images are all protected by copyright)
Given the comics' precedent that there is no significant "upper limit" to the level of the Hulk's strength, which can reach so-called "Cosmic Levels" under the right circumstances, it's basically impossible that anything the Hulk does in the films could be considered to be "too strong for the character", for similar reasons[*].
Where the movies tend to fail is in over-simplifying or misunderstanding the Hulk's many weaknesses.
[* Actually, since the Hulk in The Incredible Hulk movie appears to have closer ties to "Ultimate Hulk" – a creature born of a mutated gamma-irradiated version of Captain America's Super Solider Serum, there probably is a more reasonable upper power limit, we just haven't come close to hitting it yet.]
Were the Hulk movies accurate in portraying Hulk's strength?
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