Why didn't the First and Second Hokage's fight with full power against the Third? When revived by Orochimaru, the First and Second were sent to fight the Third, however, we know today that:


   The First beat one of the most powerful ninjas in history (me), could heal himself without activating any special jutsu, could summon a freaking chakra sucking tree dragon.


Moreover!


   The Second had known (invented!!) Edo Tensei (meaning he could have broken free of Orochimaru's control), he also knew space-time ninjutsu.


With those abilities, plus immortality, they couldn't have possibly lost against the Third at their full power.

So in that case, why didn't they use their full power against the Third? Their emotions should have been completely erased, and made into a strict killing machine, and nothing more.
Revived or not, they're still not the real deal. The Third was not fighting against the real Shodai and Nidaime. That would have been perhaps a completely different fight. 

Besides, the fact that Orochimaru's Edo Tensei might not have been that perfect and powerful (perhaps less perfect than Kabuto's), makes me (and not just me) think he used it for the sentimental effect it would have had on the Third, i.e. fighting against your predecessors, rather than actual relying on their (weakened) power only.