I know the two dramas are very different, but I am recommending Queen Seon Deok to Fiery Priest fans because Kim Nam Gil's role as Bidam in Queen Seon Deok is simply unforgettable. Kim Nam Gil's shows both comedic and serious acting that eventually gave him his best new actor nomination at baeksang for Queen Seon Deok. He first appears in Episode 21 or 22. But I still recommend people to watch the whole drama since the whole drama is epic.
For Queen Seon Deok fans, Fiery Priest is a drama where Kim Nam Gil is the main character (you don't have to wait more than 20 episodes for him to appear). You can guarantee he gives great performance in Fiery Priest, he was after all nominated for another baeksang award for this role, he won daesang at SBS awards as well.

For new fans of Lee Tae Ri from this drama, you need to check him out in Moon Embracing the Sun. He is such an underrated actor because he was acting next to today’s popular young actors Yeo Jin Goo, Kim Yoo Jung, and Kim So Hyun but somehow wasn’t noticed by the masses unlike the other three.
The two dramas are not very similar. But Extraordinary You has a historical part where the main love triangle of two guys and one girl is featured. If you enjoyed that, you might like the historical dram Moon Embracing the Sun also, where all the other plotlines is subservient to the love and romance story. Also, if you like seeing Lee Tae Ri in historical costumes in Extraordinary You, you can see him rock those in the first six episodes of Moon Embracing the Sun as the young version of the second male lead.

Both are Joseon period dramas starring Ha Ji Won. Both also happen to be underrated historical dramas of hers in comparison to Empress Ki. I watched both these dramas next to each other and became an instant fan of Ha Ji Won. Who could imagine that the graceful Ji Ni can also be the action queen Chae Ok?

Painting plays an important part in both dramas. It’s so important since the female lead in both dramas have talents in painting. King Jeongjo features in both dramas (though he’s not the main character in Painter). Since it’s both about King Jeongjo, you expect to see a glimpse of his sadness and grief due to the early death of his father Prince Sado, political battles against his step-grandmother the wife of the former king, plus you can see a loyal minister to him named Hong Guk Young.

For Binjin fans. Hyun Bin and Son Ye Jin both appear in both shows. There is no loveline in The Negotiation but there is in Crash Landing on You. If you can't get enough of the two together, I recommend one show for fans of the other and vice versa.

They are not very similar, but both of them are Song Joong Ki's dramas. I am recommending Arthdal to SJK fans watching Vincenzo because it is a very underrated drama and I feel that SJK great performance in Arthdal needs more atttention. Aside from Song Joong Ki, Yang Kyung Won and Choi Young Joon (also in Vincenzo) also had small/supporting roles in Arthdal.
Arthdal comes in multiple seasons. As of March 16, 2021, only the first season is released. The first season is divided in parts, of which this particular show of Arthdal I am recommending is part 3.

They are not very similar, but both of them are Song Joong Ki's dramas. I am recommending Arthdal to SJK fans watching Vincenzo because it is a very underrated drama and I feel that SJK great performance in Arthdal needs more atttention. Aside from Song Joong Ki, Yang Kyung Won and Choi Young Joon (also in Vincenzo) also had small/supporting roles in Arthdal.
Arthdal comes in multiple seasons. As of March 16, 2021, only the first season is released. The first season is divided in parts, of which this particular show of Arthdal I am recommending is part 2.

They are not very similar, but both of them are Song Joong Ki's dramas. I am recommending Arthdal to SJK fans watching Vincenzo because it is a very underrated drama and I feel that SJK great performance in Arthdal needs more atttention. Aside from Song Joong Ki, Yang Kyung Won and Choi Young Joon (also in Vincenzo) also had small/supporting roles in Arthdal.
Arthdal comes in multiple seasons. As of March 16, 2021, only the first season is released. The first season is divided in parts, of which this particular show of Arthdal I am recommending is part 1.

Everyone knows Song Joong Ki from DOTS. On the other hand, this extremely underrated drama that he did in 2019 called Arthdal Chronicles deserves way more love and attention, thus I am recommending Arthdal to SJK fans who became fans from DOTS. Arthdal Chronicles comes in multiple seasons. As of March 16, 2021, only the first season is released. This is part 3 of the first season.

Everyone knows Song Joong Ki from DOTS. On the other hand, this extremely underrated drama that he did in 2019 called Arthdal Chronicles deserves way more love and attention, thus I am recommending Arthdal to SJK fans who became fans from DOTS. Arthdal Chronicles comes in multiple seasons. As of March 16, 2021, only the first season is released. This is part 2 of the first season.

Everyone knows Song Joong Ki from DOTS. On the other hand, this extremely underrated drama that he did in 2019 called Arthdal Chronicles deserves way more love and attention, thus I am recommending Arthdal to SJK fans who became fans from DOTS. Arthdal Chronicles comes in multiple seasons. As of March 16, 2021, only the first season is released. This is part 1 of the first season.

The dramas are not very similar but they are the only dramas (as of 2021) that is set in historical times where Han Hyo Joo is the female lead. While her character in Iljimae is a rich noblewoman compared to her lowborn character in Dongyi though, both her characters are depicted as nice, kind, and good-hearted. Another similarity of both dramas is that Kim Yoo Jung plays the child actress of Han Hyo Joo in both dramas.
(Including Kim Yoo Jung's characters in Moon Embracing the Sun and Grudge the Revolt of Gumiho and Han Hyo Joo's Shining Inheritance character, I somehow feel like those two actresses are the go-to of casting directors back then (2008-2012) when they needed someone to play the kind, noble, and good-hearted beautiful female lead (basically a Cinderella like character).