Depends on what you like about EO. EO makes party building and finding synergy a core part of it's gameplay. For something like that, Star crawlers, Paper Sorcerer, and Wizardry 8 are good choices (7th Dragon series also falls under this, though it's not first-person).

If the mapping is what you like, I don't think there are any other games that integrate it into the game itself, but a lot of games expect the player to map using graph paper. For those, Wizardry 1-3 are good to start with as they are challenging but always fit on a 20 x 20 grid. Later Wizardry 5-7 are also very good but have larger maps that will end up going off the edge of the paper sometimes (though they tend to have more interesting combat too). Might and Magic III would also be a good choice if you want to do more than dungeon crawl. If you do try classic Wizardry, I'd recommend one of the console ports. Robert Woodhead (programming of Wizardry on Apple II) has actually said the Famicom version is the "best". I'd say the GBC or SNES version are best.

For something more modern but still like Wizardry, there's Elminage. It's a modern take on Wizardry from a dev that actually made a lot of Wizardry spin-offs. It has more interesting classes that classic Wizardry. Experience also has some modern takes on the formula (Undernauts being the most recent) but I have trouble getting past the aesthetics of them.

Finally, if you want something more tactical and don't mind AD&D, take a look at some of the gold box games like Pool of Radiance. Dark Heart of Uukrul probably falls in here too (but is not D&D). They have first person mazes, but grid based combat, sort of like a proto version of Tactics Ogre.

And my final off-the-wall recommendation is Legend of Legacy. It's not first person, but it has the same explore, map, and push your limit loop as a good DRPG.