technical vanilla: toss up between ac4 [dat water] and bf4 [shanghai, again that water]
beautiful vanilla: the witcher 2, because whilst the plot and gameplay havent hooked me, i'll admit its very beautiful albeit somewhat overwhelming at times with some settings
modded: skyrim, hands down
inspiring: kerbal space program because some of the orbital views around jool [when multiple moons are in view] are amazing, or possibly relieving given the effort to get there
overall though modded skyrim has it for me, once spent 5 whole minutes staring at a tree stump in riverwood it was so beautiful