GM's 3800 and Ford's 300 I-6 are two engines that I think fall under the unsung heroes category, in that they are both low end torquey engines that don't ever seem to want to give up. It's sad they stopped production in '06, which ended the 39 year reign of an excellent engine. I just read the wikipedia article for
the Buick 3.8L here, and it has a very interesting history. It's very similar with the 3.0L Nissan engine, which IIRC had the ability to support 600HP with the proper heads etc.
I understand progress is necessary, but some things need not be replaced, only slightly altered to keep up with the times.