Yeah, DMC4 stands to me as the best DMC design-wise. Vibrant colors when needed, bleak colors on darker places, labs have that futuristic feel, DAT BLIZZARD.
However, I must say that people give DMC3 little credit. While it had worse visuals, each area felt pretty damn unique, and the areas after Leviathan are all incredibly pretty. Not to mention the demon world was creative as hell and DmC takes many of it's ideas from that.
To me it goes DMC4>3>DMC=DmC>>>>>>>>>>>>>>>>>>>DMC2.
DmC had some cool stuff here and there, but too much bloom and having areas being mostly red, or mostly blue, and having too much oof the "WORLD IS OPENING, CRACKS AND FLOATING ROCKS AND **** YO" syndrome. DMC1 felt creepy, but the areas weren't all that great IMO.
DMC2 began fine, then we got to the city and it became crap.
Dmc4 was the worst. Good graphics but very un dmc environments, and not many of them. The blizzard was coil but the forest was out of a different game and the labs were dull. The castle was like dmc 1s without any of the erie creepiness