Hiya Wardy
There seems to be very little valid research into the correlation between long-term memory and 'intelligence' (whatever that might really be).
However, Ackerman, Beier, and Boyle's report on Working Memory and Intelligence�Their Correlation and Their Relation found a positive correlation between short-term memory (referred to as 'working memory capacity') and measures of intelligence (defined in their report as 'cognitive ability measures'). Their research has been challenged by a published comment from Oberauer, Schulze, Wilhelm & S�� but the basic principles seem to hold true.
In everyday terms, the ability to store plenty of data (for further analysis) would seem to be a prerequisite for successful completion of advanced tasks measuring cognitive ability. However, whether such tests measure 'true' intelligence is open to question.
Chris