Hate to hark on this again, but metro 2033 on PC ran quite well for what it was graphically doing (minus one option, the advanced depth of field).
So many of the lights were volumetric, so many of the lights cast shadows, the shadow resolution was huge, full screen effects were done at native resolution... etc...
While metro last light added lots of great graphical features (the bokeh, the tesselation on nearly everything (which will be improved in redux), the new particle lighting) and of course tightened up the code to make effects run better, it also removed and toned down some of the sample counts.
Shadows are not as high res, there are less volumetric lights, the volumetric lights do not appear to run at native res, etc...