I like Oni because I never have to fear for his life, since he's so tanky and has a broken fast regen time. He's also insanely strong offensively, and it is truly awesome to see him raze down wave after wave (basically) of enemies with his flaming katanas. Also, he looks the coolest out of all the KR heroes. I know he's hopelessly OP, so I can't respect him from an objective perspective of game balance like I want to be able to do with every hero; but at the same time, he's too cool to not be my favorite KR1 hero.
Alric is just really awesome. His statistical passives make him my "least favorite favorite" hero, but the good abilities that he does have, plus how epic his appearance is and how atmospheric his quotes are, are all so good that he has to be one of my favorite heroes.
Reg'son is my supreme favorite KR hero of all time for many reasons, the most noticeable of which follow: 1) He's well balanced (:yey:), 2) he's awesome to look at, and 3) he has tons of personality and a cool background.
Obviously, the short summaries above are just that, summaries. If I were to list everything I like and dislike about these heroes from an objective and subjective perspective and then explain how I weigh the pros and cons of them against each other in my mind, it would take a lot longer to write. I'll save that for a later date, when I can write detailed reviews for each and every one of the heroes in the KR franchise.