Do you know of obscure or underrated fantasy RPGs?

Whilst not really obscure, more off genre, Star Wolves provides an excellent RPG experience in a non traditional space (no pun intended).

Edit : Sorry, just saw you were after Fantasy.

Something a bit older an a little less known is Dink Smallwood.

Any particular sub-genre?

If you like FPV multi-party dungeon crawlers, with just a hint of city building, I really liked Heroes of a Broken Land (currently 75% off / $3,74 on Steam)

https://store.steampowered.com/app/314470/Heroes_of_a_Broken_Land/

The graphics are pretty bad, but I quite enjoyed the party building / leveling / dungeon components. Was one of my favorite games in 2018, and definitely would seem to meet the 'obscure' criteria.

Do you mean Dink Smallwood?

Yep - no idea where Dinkwood came from. Cheers. Edited.

No worries. I'm not a stickler. I figure anything people bring up might turn someone on to something unexpected.

Currently I'm playing Drakensang and absolutely love it. Sure, it has some "warts" but the atmosphere is wonderful, the graphics are a "classic storybook" style, the characters are fun, and (my big interest) there are a lot of AI companions! Sure, sometimes they get "confused" and fail to fight in nearby combat, but I can live with it. I've enjoyed some time recently with Blackgaurds II, but Drakensang is The Dark Eye game I wanted... although I will definitely be playing the Realms of Arkania games sooner-than-later.

I have heard of it, but only recently. What do you enjoy about the games? I'd guess the story...?

The entire world; how the people deal with the situation of living in an underground prison cave in multifaceted ways, without going too grimdark.

Personally I really like the SaGa series (I am re-playing the SaGa 3 remake right now, actually).

SaGa Frontier 2 and the Romancing SaGas are all fantasy settings. (Romancing SaGa's setting feels like ancient mythology, complete with a pantheon of gods and many different regions; SaGa Frontier 2 is a common magic setting (almost everyone can use magic, and the one time a major character can't, it's a major plot point), and there's no sign of the divine (not even worship of such a thing; the one cult in the game worships something else).)

SaGa 1 starts out like a fantasy RPG, but it doesn't stay that way. SaGa 2 feels like a fantasy RPG, except that there are guns and playable robots. SaGa 3 has a plot involving time travel.

SaGa Frontier is, well, all over the place when it comes to setting. If you play as Blue, you will see a more magical fantasy side, while playing as T260 is basically a cyberpunk setting, complete with a couple scenes where you go inside a computer system. It probably has the most diverse setting of any CRPG I've played.

I do not know what Unlimited SaGa is like setting-wise, as I haven't played it. I hear it has guns as a weapon type and one of the main character choices is a pirate.

(Be aware that these games deviate from the usual conventions of the RPG genre; you won't find things like levels and experience points here unless you are playing the original SaGa 3, for example.)

I have always liked Driftmoon.
It is a very charming game. But be aware that it is quite short.

I thought of another: Dragon Wars.

While it's sometimes been considered a successor to the Bard's Tale series, it's actually very different. You have a classless skill point system for raising skills, the game is non-linear, and the game is not focused on dungeon crawling and fighting monsters (though there's still some of that). Rather, there's a heavy emphasis on adventure-game style puzzles to solve using the various skills you've learned and items/spells you found (note that this aspect of the game feels reasonably fair and not the sort of thing you'll get stuck on for ages). Many puzzles in this game even have multiple solutions; there are plenty of ways to escape Purgatory (one of which is only possible on New Game +),

Wait, did I say New Game + for a game released in 1989? Yes, I did indeed.

The Dark Heart of Uukrul
Disciples of Steel
Nahlakh
The Aethra Chronicles: Volume One - Celystra's Bane
Natuk
Aleshar: The World of Ice

Oldschool
Albion
Rage of Mages 1 + 2, as well as Evil Islands
Vagrant Story (on Playstation, a classic but not much talked about, footage)

Indie
Knights of the Chalice
Fortune Summoners - Secret of the Elemental Stone (platform action indie JRPG, Town Footage, Combat Footage)

Freeware
Dark Disciples 1 + 2 (Footage)
Dark Age 1 - The Continents (Footage)

Not fantasy-themed
The Spirit Engine 1 + 2 (Footage)
Space Funeral (RPGMaker, Footage)
Die Reise ins All (RPGMaker, German only - sadly, because it's one of the best RPGMaker games or even JRPGs I've ever played, Trailer)
Teudogar and the Alliance with Rome (never played it, Footage in Russian ... although I think the dev was German)

Ohh yes, this one is sensationally unique. One of my favourites.

Also in the old school, Spirit of Excalibur and Conan the Cimmerian are excellent fantasy RPGs.