Infinity Engine games are garbage, so you probably won't enjoy actual good games. Still, here are some of my favorites.
Ultima IV was the game that introduced me to CRPGs back when I was a consoletard a decade ago. It was the Master System port though, which is not ideal for seasoned players, but perfect for beginners. It has outstanding exploration, a great plot, and very innovative simulationist design philosophies, but it also has shitty combat, little to no challenge after the initial struggle, and poor customization options. Still one of the best games ever, but avoid it if you're a combatfag.
Ultima V has much better mechanics, balance, combat, and quality of life features, and it's a fun and challenging game till the very end, but it also axed the virtue system from the previous game. The plot is good for 1988 standards and NPCs are better written, but this is not necessarily a good thing in this game, as it makes talking with NPCs more frustrating, as it's easy to miss some clues. Still, this one feels as a huge improvement.
Sword of the Samurai is an RPG/strategy/arcade hybrid, where you compete with other clans to become shogun. It has a nice historical setting, a good reputation system, and many non-scripted "evil" options (you can assassinate rivals, kidnap their relatives, betray allies, and so on) which may or may not affect your karma. A must play game if you already like other historical games like Darklands, Pirates! or Expeditions: Conquistador, or if you like Kurosawa films, as this feels like a homage to Ran.
Darklands is the only RTwP game worth playing (besides Planescape: Torment, which is a good storyfag game despite its mechanics), and a big FUCK YOU to the generic AD&D games from that era (not unlike Fallout 5 years later). Very detailed historical setting and simulationist mechanics, infinite sandbox quests, and very interesting customization options. RTFM, as it's one of the best ever written.
Realms of Arkania is a hardcore simulationfaggotry, with tons of customization options and spells which affect way more than just combat (including negative attributes, social skills, nature skills). Not necessarily a hard game though, and combat is kind of crap. You can safely skip the first game and start playing Star Trail, since both games are very similar, but the sequel is way more polished and has an actual plot.
Ultima Underworld is still one of the most immersive RPGs ever, this game is a huge achievement way beyond being the first of its kind. If you like games like Morrowind, Arx Fatalix or Gothic, give this one a chance.
Telengard is a fun little arcadish dungeon romp, a very simple (and brutal) game without actual objectives. I don't know why I keep coming back to it.
Alter Ego is a modern life simulator, with character creation and customization, skillchecks, and C&C. It's a very well written game, and in my opinion, an early example of RPG without combat, take that Disco Communism.
Dragon Wars mixes well crafted blobber combat and exploration with more modern RPG mechanics an concepts from Wasteland, like different ways to solve quests, skillchecks, a less derivative setting, and a more involving plot. A must play game.
Might and Magic: World of Xeen is casual stuff, but very charming casual stuff. It's a very well made open-world exploration game with engaging and very fast turn-based combat. Earlier M&M games are actaully more engaging and challenging, but this one is the most polished one, and the easier to get into if you're not a fan of classic blobbers.
Wizardry: Proving Grounds of the Mad Overlord is still the definitive blobber though, a dungeon survival game with very polished and well-thought-out mechanics, and very exciting gameplay despite its age. It has excellent NES and SNES ports if you can't stand ancient GUIs.