Hmm I'll agree WGU has an epic feel, not the least of which for that end visual of the crash against the mountain.
Chronoscope, especially the way it begins and the way it ends with the tent disintegrating has a monumental feel.
White Plume Mountain (primarily for the Giant Crab fight) and to a lesser extent the Price of Freedom for its Prison-escape genre and sheer scope. (I don't even like that quest.)
I'll say they missed a major opportunity with Immortality Lessons... it could have felt truly epic if we had been able to climb that ice stairway and had the adventure included more of the outside of the castle the way you can go in and outside the Prison in Price of Freedom or outside the glacier in WGU really, and truly adds to the immersion.
The Final Enemy had moments of epicness as did Rest for the Night, and Swim at your own Risk.
Captive of the Hidden God, easily epic with the first real sight of Vecna.
Parts of Temple of Elemental Evil feel very epic, I happen to personally like it better now that its in bite size pieces.
Into the Deep still feels special even with new underwater quests available.
Plane of Night is perhaps one of the most epic experiences in the game even still, and a landmark experience for every new player.
Invitation to Dinner cannot be overlooked. Sealed in Amber still has a very epic atmosphere despite alterations to the quest. Sunrise as a prelude to the Strahd Raid has moments that feel epic.
Of course the Strahd raid is mind-blowing... but also has moments of really? really?! (stairs)
Diplomatic Impunity has that moment when you look down on the beach and see the invading force... if only they had done something with that as an optional in the Legendary version. Not enough to count I suppose. Likewise as fun as it is to blow up ships in Blockade Buster and Tide Turns, the whole of those quests don't feel particularly epic.
Gianthold Tor still feels epic, primarily for the optional dragon fights and to a lesser degree Prison of the Planes.
Subversion and all of Necro4 feel epic.
In the Flesh, I mean that end fight is an experience unto itself.
Desire in the Dark, Three Paths to Battle, Beyond the Rift, and some parts of Sharn such as Reach for the Sky very epic either for atmosphere or situation.
Beyond level 16 there is more that feels epic than doesn't and I don't want to list that much.