Any of them before soil depletion and banana blight. Fruits and veggies tasted so much better in the 80s. Melons in particular taste lifeless now. Once in a while I strike gold at the local farmer's market or in our own garden.
That said, heirlooms do have all kinds of crazy flavors and differences.
Yeah, I'd bet that some of them don't last as long as the standard red tomatoes that you get in the store, but looking through heirloom tomatoes is kind of a trip, from a visual standpoint. Grocery stores seem to have pretty much standardized on about three red ones -- and I'm not saying that they're bad, but it does kind of mean that people don't get to see a lot of variety. Unfortunately, I'm not a huge fan of just eating tomatoes plain, so never got super-interested in obtaining them, but they do look damned cool.
That's pretty much the case with any produce at the grocery store these days. It's all picked too green. It makes me sad because I haven't had a legit ripe avocado in ages.