Terms like "realistic" are very much subjective and a totally overused word in the context of video games. And some people notice and appreciate graphical details more than others.
I think it is fair to say that vanilla Skyrim looks pretty good out of the box. The character models and faces are 5 million times better than Oblivion, the landscapes are equal to better, IMO. OB was good in that respect. The climate in Skyrim is vastly different than in Cyrodiil, so the color palette Bethesda chose for Skyrim is a pretty fitting one. I personally liked Oblivion colors more, but I like the winter less than the summer, so there you go. I think Bethesda made overall very good choices.
Now for the gamers so inclined, you can finetune the graphics really any way you want, and the engine is quite tolerant in what you can load up and still have a stable and well-running game. So kudos for that.
I for once notice the SMIM changes a lot, I think it really makes a stunning difference and has become "essential" for me. Outside of that, I just have the official Hi-Res DLC's plus Unofficial Patch for that. I have the WATER mod and I also have Skyrim Flora Overhaul, plus Phinix Natural ENB. That's about it. I started loading up on all sorts of extra HD textures and stuff for weapons, clutter, potions, cothing but came to the conclusion it strains my system too much for mostly marginal gain in visual enhancement. Of course, a strictly personal opinion. If I had to settle on only something, I would not let go of SMIM and Phinix ENB.