Burn me on the stake as a heretic if you must, but I think a full frame dSLR comes the closest.
Before the flames get me, a few explanatory notes:
- Purely talking in terms of the equivalence of the experience between the film camera and the digital camera. I have in mind a Nikon d700/d800 compared to a F100.
- Full frame for the size of the viewfinder view and lens equivalence and the whole OVF experience.
- Not talking about which cameras are most satisfying to use
- The ergonomics and control system of the Dx00 and the F100 are very similar. All the basics (shutter speed, aperture, AF, frame advance) are easily changed without need for looking at the rear LCD or going into menus.
- I am not comparing the experience of a dSLR compared to an F3, FM2 etc.
- Battery life is long enough on those dSLR that it doesn't intrude on the experience too much
- Reliability and weather sealing mean you can treat the digital version much the same as the film version.
So basically most of the time can forget whether you are using a digital or film camera and get on with shooting.
In my opinion M8 comes close to the film experience, but it's digital presence intrudes more often. To its credit it does produce very nice files which need v little processing, I can imagine the M240 gets closer experience wise.