I don’t know a ton about foreign motors other than surface level stuff like the 2JZ, Wankel, etc. so please forgive my ignorance outside of US motors.
However, in my eyes, it doesn’t get better than the simplicity and easily available power of the SBC, BBC, and 6BT. What are your all time favorites and why?
The Mercedes M119 V8 from the early 90s. Great sound, beefy internals, and easy power without major issues.
Honorable mention goes to the Mercedes-Cosworth 16-valve 4-cylinder used on the 190E 2.3-16, but those engines need to be maintained very well or else they get fussy.