Bioshock Infinite for sure, at least the first hour. The entrance into Columbia is seared into my mind. What an incredible moment, if only everything that came after was as good.
H:ZD as well. I was completely taken aback once I was finally let loose in the world. Spent at least an hour just strolling around. I can't wait to dive back in for the Frozen Wilds. Snowy areas are my jam.
Honorable mention to TERA Online, entirely forgettable for the most part, but for a brief shining moment, one tiny little area tucked away off the beaten path caught me completely off guard; the Heartwood. Took me right out of my quest grinding flow to stop and admire the scenery. Pretty much the high point of that game as I quit not long after.