I wouldn't go that far. It depends on what the engine was designed for. Most typical automotive engines were not really designed for continuous duty, but there are plenty of other engines that are. Those used in remote industrial sites to power equipment run for years and years without failures. Yes, most are typically designed with diesel fuel in mind as it's easier and safer to keep them fueled, but some run on other fuels and have proven quite reliable as well. Though, the same can be said of electric motors designed for the same abuse. I would say in the proper application, the failure rates i've seen would put properly designed engines as more reliable than electric motors, given the same environments.