Hmmm. Your use of the word “isn’t” denotes you’re referring to the combination of the two items, and if that is so, my answer is no, that is in no way the best, nor is it even a close contender for that superlative. However, if the word should have been “aren’t” as opposed to “isn’t”, then you’d be referring to the two items separately. My answer in that case would be that both ice cream and bacon are very good in their own right, and that the superlative can be applied to each of them, but of course one has to take into account the context. To blindly call them the best without comparative examples is a bit difficult to imagine.
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