At least to me its one of the more epic moments in CV and at same time one of the more well balanced fights VS a human enemy (I didnt played any of the 3D games until the end, only played 1 hour more or less, also I didnt played OOE until the end).
If they did all bosses and enemies with a AI so good it will be wonderful.
*SPOILER ALERTS REGARDING ARIA OF SORROW*
Honestly "epic" gets tossed around so much it's lost its meaning, and has even been bastardized into a meme (epic [insert word]), but the Julius fight truly is one of the most epic Castlevania moments, and for so many reasons. I know some of my friends strongly disliked the pale-skinned, white-haired, glowing, effeminate-looking Belmonts and Belmont-clones, and to them Julius was a return to the ass-kicking Belmonts they grew up with, especially since Julius has such an epic soundtrack to accompany him.
From a boss perspective, I completely agree with you and honest-to-God put Julius as the best example of fighting an awesome "human" boss. There are no transformations, no minions, and no frustrating, tedious, boring, repetitive pattern to memorize. Julius on the other hand is an in-your-face, back-and-forth slugfest, and a damn exciting one at that. And, JUST when you think you've got Julius by the balls, he breaks out Grand Cross in the most epic manner since Richter, and starts using sub-weapons. And no matter how many times you face him, he's still fun. Go fight Galamoth on SotN or that giant Centaur from OoE, then compare them to the Julius fight and you'll know what I mean.
And from a lore perspective, this was another epic moment. Aria had such a delicious twist about YOU the player being Dracula, even though Soma is trying to resist that influence. Not only are players still digesting the knowledge that they are playing as the series' primary villain, they come face-to-face with a Belmont. All throughout the series we've been cheering them on, and in any other circumstance we'd be cracking our neck in preparation for the final battle. Instead, we--"Dracula"--are now facing a Belmont--the usual hero--except we';re not controlling the "good guy". To go even further with the lore, this is (as far as I understand) the first time that "Dracula" has ever won a main fight against the Belmonts, although Julius and Soma both point out that Julius was holding back.