I vote the DB-3 first.  More prominent level bomber for the Soviets in WWII, carried 5500 lbs of ord.  Then, the IL-4 would be my second best.  
The Tu-2 and even the Pe-2 would not be bad, but the DB-3 would be best.  It was to the Soviets as the B17 was to the US.  The IL-4 would be to the Soviets as the B24 would be to the US.