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?
Budget V8: Gen iv/v SBC truck engines. Grab any of them out of a yard, throw it into a classic muscle car with headers, car intake, and tiny cam, and you’ve got 400-500hp with the same torque the old engine had. And it uses half the fuel.
Gucci V8: tricked up aluminum 416 or larger Gen iv/v SBC. 500ft/lbs, 550+hp, 6500+rpm, light weight.
If you’re into cool engineering: Gen 3 Coyote. 8k rpm with just a set of oil pump gears, stock internals can take about 1200hp reliably, and also 8k rpm. The fueling tricks you can do are pretty sweet, as well.
Basic turbo 4: Ecoboost 2.0. A couple basic mods will get you to a healthy 350hp, and you can still justify that in a DD.