I will try to make a very short list covering the essential, must play CRPG's. But behold! Rpg is a genre that needs focus and carefulness. You simply can't play a rpg and another 3 games, i.e, because the chances are that you will lose focus and will tend to dump the game in the middle of the campaign. I think this is a serious error if the game is good enough to warrant a completion.
I tend to play only one game (and, sometimes, It's worthy to focus on only one souce of entertainment at a time, so, if I am watching a great TV series or reading a exceptional historical book, maybe it's better to focus only in one thing, because you will finish quickly and you will dive deeper)). So, you should really question yourself if you want to focus that kind of attention demanding undertaking.
1) Baldur's Gate 2: Shadows of Amn. This game represents the isometric approach of rpgs, which is my favourite one because it covers a nice tactical perspective. The combat system is very good here, it uses the glorious 2nd edition of AD&D and have one of the best mage battles in computer history. The narrative is on point. The exploration is not as good as the first one, but it's there. The character progression is very nice, you really start to feel that you are becoming a god chosen one. If you want a newer title in the same vein, you can try out Pillars of Eternity 2: Deadfire.
2) Fallout: New Vegas. Forget Bethesda, the best newer Fallout was created by Josh Sawyer from Obsidian Entertainment. This is a huge rpg experience, with momorable npc's and factions. The exploration aspect of the classic rpg's characteristcs is here, and it's one of the best, if not simply the best, of the newer generation games. Your choices will have consequences later on (and this is a great statement, since the majority of titles that claim to have a C&C system is simply a scam or borderline cosmetic flavor). The combat is not tactical, which is a huge downside in my book, but everything else is simply the best the genre can offer.
3) Dragons Dogma: Dark Arisen. Do you want a good action combat in your rpg? With a rare open world feature that it is actual worth exploring? What about a action combat system with a party? This games has it all. Dark Souls has the better action combat, but doesnt have the other rpgs mechanics worth mentioning, and Dragon Age: Origins, although very good, sometimes is just too simple to follow up. Both are great games though, but if a short list should be made, I think Dragons Dogma is the better RPG.
4) Wizardry 8. We simply cant make a list of must play rpgs without mentioning the worthy dungeon crawler with first person perspective niche subgenre. This game is very difficult to a novice, but this is a great thing to me. Who cares about easy, bland games, right? Here, you will need a mod to speed things up, because this game is all about dungeneering and battles, but animations make things slow here. Wiz 8 has the best party creation and party progression in the crpg genre (maybe wiz 7 is even better, but too damn old for novices to care). You will need lots of resolve to finish it. This is a great thing, because newer games, with great and rare exceptions, almost play themselves to the end, without any real challenge. A rpg should be challenging.
5) Vampire The Masquerade - Bloodlines. Well, we need a good story/narrative-heavy rpg to put in this list. The best story in a rpg is definetly Planescape Torment. But I already focused on Baldur's Gate to represent the infinity engine rpgs. And even Planescape, althoug having the best global story, does not have a better classy on point writing as this game. I think the setting is better here too. Bloodlines will let you role play your character better as well, since you will need some playthroughs to see most things, which screams what a RPG should always convey to me. You really should read more about this game, because in few lines I will not accomplish much. But, as all three troika games, this game is a broken mess riddle with bugs. You will need some fan made patches. Just understan this. If you want to watch a video about it, I recommend this:
Unpopular opinion: The Witcher 3 is a great cinematic experience (especially the DLC's), but the rpg elements are extremely bland and the quest markers with a gps make the exploration simply non existent in this game, which is a shame. The combat becomes uber easy later on (attack, roll, stun with ward rune, repeat), but some enemies are fun to kill, like that Griffins in the beginning. The story is nice, but if you want story, read the books or watch the Netflix series imo, if you dont have much time.