I see. The stock game looks pretty good to me and its a pretty immersive world.
So far, working out which mods I can use with which others, for a new mod-heavy install (after several false starts), Static Mesh Improvement Mod, Book Covers Skyrim, and HiRes Legible Roadsigns, have been the extent of graphics detail mods I've added, so far, and it's all been good. For imagery based immersion, Climates of Tamriel or Realistic Lighting Overhaul are going to do more for gameplay than any of the high res stuff.
The better mods, for me are mods like climates or sound, lighting effects, things that focus on immersion. The result of all of this together is more of an overall presentation--you aren't going to be wowed by walking around and zooming in on grass and rocks and such, but after spending a few hours in this world as you go from climate to climate, it really starts to come alive in a way that you can't experience outside of a PC
P.S. To give an idea of just that...when I got to around 120 plugins, with PerMa+SkyRe (all but main) appearing to be working OK, did I run off to Whiterun in a new game, slay that first easy dragon, then head up the mountain? No. I wasted 2-3 hours harvesting plants for later potions and poisons, plus hunting foxes, elk, and bear, to make some preferred cloaks, camping gear, and armor items (no auto-aim, tweaked arrow/bolt flight angles in skyrim.ini, complete crafting overhaul, winter is coming, cloaks of skyrim, frostfall, ineed, herbal tea...).