Motorcycle engines are largely not scaled down car engines tuned for performance at the expense of reliability. They are designs built from scratch under different constraints. A mid-level motorcycle engine from a Japanese manufacturer should last longer than a mid-level car from a Japanese manufacturer, all else being equal.

There are motorcycles that you buy facing the near certainty that it will most likely outlive you, like KLR 650, or you can get a Ducati with a Desmosedici Stradale in it, where you have to get valves adjusted (major service) every 2500 miles. But given timely service, no motorcycle will last less than 50k miles, and most will last above 100 before an engine block rebuild.

Comparing cars to cars, or motorcycles to motorcycles, the logic holds though.