As far as i know - this depends on the Engine technologies used, so earlier it was the carburetors, then EFI, then VVT-i and now even newer technologies are used with on going improvements so the latest models are to be lasted a lot longer.
on the second note, its hard just to decide the engine condition from the mileage that had been done. it depends on how the engine had been maintained, and cared. simple example would be our selfs - depending on the food that we take - healthy or unhealthy, exercise we do, things we do will determine how well we would be isnt it? cant tell from the age nah? u can be older but at the same time be stronger if had well maintained.
and petrol cars can go to 300-400K mileage without problem (if maintained good), and even more may be with a engine rebuild.