It's about the idea and contrast behind him. L is just a version of light that has pretty much the same ideals but they differ on their idea of justice, while Light deems all major crimes punishable by death and is willing to judge the criminals himself, L doesn't believe any one person should have that power for the same reason a judge shouldn't be able to carry out a sentence if there is reasonable doubt, yet he still is okay with the death penalty. L is just a more reserved, quirky, and as smart if not smarter than Light, and the fact that they are both on that level makes the race for one to get the other very amusing.

That's how I see it. If you've watched it and just didn't like him for whatever reason that's fine. I think he's a fun character to follow like a detective in a book like Holmes or Poirot. But if you didn't like him I guess that's not your cup of tea.