I'm proud to say that I was never one who thought 80s era engines were the pinnacle of anything other than being a cobbled up mess of band aids and shortcuts trying to meet emissions standards. 
As I said in my post, the low hanging fruit has been picked. Todays engines are manufactured to more precise tolerances, with better alloys but at the end of the day, that slug that slides up and down in the bore of the engine only makes power for part of one trip. All the other three trips use energy and wear things out. A reciprocating engine will never be able to overcome that.