There was a time when first-person dungeon crawlers were all the rage, from classics like Might And Magic III: Isles Of Terra to the simply titled Dungeon Master.
It shouldn't come as much surprise that D&D got in on this action, and the Eye Of The Beholder series surprisingly still holds up fairly well to this day -- although not without flaws and serious signs of aging.
Going outside the typical Forgotten Realms game, this same idea was presented in the gothic horror titles Ravenloft: Strahd's Possession and Ravenloft: Stone Prophet.
If you dig the first-person style of the Wizardry series, then these are worth playing, and they are an interesting look back at where the genre started for fans of newer titles like Legend Of Grimrock.
Coming out not long before the stellar Baldur's Gate, there was also the first person, real-time entry Descent To Undermountain, which was along the lines of The Elder Scrolls: Daggerfall, but much more poorly received.