I don't know if Shadow of Colossus from the Playstation 2 is considered RPG(there's not much character development) but given its solitary atmosphere in the wild, its one of my best moments in a fantasy world. You somewhat feel you are really alone in that vast plain, you ride a horse travelling far and wide, and the dungeons/caves, actually, every environment is unique that really makes you feel like watching a movie yet solitarily exploring old forsaken, giant underground places. also due to its art direction and storyline, it has a good consistency to keep the world believable and nothing to spoil its experience like maybe a dancing gorilla popping from no where. it gives you a gritty, adventurous feeling unlike Skyrim which was repetitive in most of its dungeon settings.
the girl you're suppose to rescue is in some sort of coma state, and after travelling a long journey to find something hidden, you claim your reward - a chance to fight a Giant, 10 storey high foe. its different setting in each of them, which makes it really fun to explore, its exciting to find out where and what to uncover.
at crossroads you'll travel across familiar paths but after that, either you'll enter an underground valley like the size of Moria Mines in lotr or fight an underwater giant seamonster. its some of the best experiences in gaming, other than Half Life / Portal :D but take note, its old though, so graphics may not be as what you expected today, but then again, very few games can give you that kind of experiences.