The “Fonline” engine fodev.net or fonline.ru was (almost) able to create a fully functional Fallout game, with zoom, higher resolution sprites or isometric 3D models, whilst retaining the look, feel and controls of the originals.

The main problem (from my perspective) was that it was designed as a “multiplayer-first” engine with real-time pew-pew-pew combat, and getting it to do anything singleplayer and turn-based needed quite a lot of work at the time - and engine updates weren’t often backwards compatible, and the documentation was often only in Russian. A lot of half-finished projects showed great promise, but then broke and fizzled out.

I think it’s still in development. Last time I looked, they were “refactoring” all the code (including fixing all the single-player stuff). It still holds promise for the future.