NJO at it's best was meh. In all honesty, the post...past a certain point in the timeline, I guess, the only Legends storyline that I really became invested in was Legacy. Darth Krayt was a great villain, rather old school in a way that appealed to my 90s kid sensibilities, and much of the main Sith characters were more of the same. Especially Darth Maladi. I mean, sure, a lot of my guy friends preferred Darth Talon - because no shit, she's practically a Dark Eldar succubus - but I preferred Darth Maladi.
And of course, Cade Skywalker. To me, he was the 90s anti-hero (ironic, considering Legacy came out in the 2010s) of the entire setting, being gruff, rude, even selfish, but also trying to find himself, before eventually deciding to choose the side of good but without going all soy boy and staying the same standoffish, grumpy, but also loyal and dependable son of a bitch we all came to love. Oh, and Princess Marasiah, of course, carrying on the tradition of actually being a believably strong - in more ways than one, being a princess and the heiress to the Imperial Throne as well as an Imperial Knight - woman in the footsteps of Mara Jade and Princess Leia (who is actually her ancestor) without being in your face about it the way Disney Star Wars loves their female leads.
Oh, and a touch of courtly love (and eventually actual romance) there as well, considering her relationship with Antares Draco.