Visually the 3d in Monkey island 4 is dated, and low poly , but I love the feeling of dimension and enclosure that 3d environments create.
Visually speaking its nothing too great, but the feeling of the 3D and being able to follow shadows to every corner and to be able to follow the light bending around corners and seeing light on the polies in front of you as they move , makes the graphics in MI 4 rather enjoyable for me, even though dated.
Now the 3d technology is even greater. Imagine the lighting , and sense of atmosphere they can now create. The movement in 4 was hated, but how often is it considered that the movement was more of a player advantage and interactivity bit than the previous game due to 3d environments ? There were more "established " "rendered" plains to walk onto, and more interactivity, game play . I feel that the key control helped making navigating these 3d environments more of a whole experience. Sure it was different, and not the same and frustrating at first but over all I liked the feeling of the graphics in MI-4 even though dated.
I feel that 3d graphics if at all presentable create an entirely different and evolved sense of dimension , and life like game play.