I have seen a car in my shop with over 300K and still looks liek it had 60K on it and I have seen motorcycles with 60K that still ran great.
Now the bikes I know with high miles were V-Twins, not some high reving kid owned 4cyl.
So like a car, a bike will last as long as someone takes care of it the RIGHT way. BUT it seems V-Twins last longer. That could be the lower power band in the RPM, USUALLY more mature rider that takes care of it (maintaince AND riding), etc...
OLD, and I mean OLD, harleys (and probable most other bike) would only last 10-15K befored needing major rework. When Harley came out with the evolution (sp?) motor they went from a 10K breakdown to 100K over night. The later Evo motors got better and the current Twin-Cam Harley motors are even miles ahead of what the first Evo's were.
So anything, for the most part, made after 1980 and been taken good care of should last 100K. But that MOSTLY depends on the rider and owner. The same can be said about a car.