By skyforbes I only have one example in mind, but it can't be that rare.
The original X-COM: UFO Defense (aka UFO: Enemy Unknown) released in 1994 had a sequel the next year, X-COM: Terror from the Deep.
Despite having the same gameplay mechanics, it was way harder, giving hard time even to a veteran from the first title.
The cause ? The game setting, switching from ground combat to (mostly) underwater combat, which mean more surface coverage, little-to-none sunlight to help you, alien terrors occurring in a ship were a maze full of potential ambush…
Do you guys have other examples ?