Legal from copyright standpoint to aggregate but not necessarily legal if the review is obsolete and you knew or reasonably should have known it's no longer applicable and it is now false as derogatory. Expect lots of hassles from manufacturers unless you have superb timely monitoring. i have no doubt someone like Google or Yahoo could aggregate and do it on a real time basis. I doubt you have that capability and so I see this as relatively risky as a business model unless you automate it and keep it current and even then expect you to have huge expenses to remove obsolete ratings.
I see no legal requirement to publicly maintain current aggregate data on a product review. So long as the data was accurate when published and the publication date of the aggregate data can be readily determined by a viewer then I see NO basis for any claim against the aggregator by the manufacturer of the reviewed product.