They look nothing alike . You can look at these two and tell yourself they look alike, but people can tell you that the creators have said that Luthor's appearance was based on Greek actor Telly Savalas and you call bullshyt?
Furthermore,
http://www.avclub.com/articles/twoface-parts-1-and-2,51399/
that nikka is brown skin with an identical hairline, he just ain't got a mustache they don't have to indentical
they made the dude brown skin because thats how he was in the extremely popular movie, don't matter who did the voice overs it ain't the first time a white person did voice overs for non white characters
show me another character in the animated series who looks like Dent with full lips, they don't draw full lips on white characters for the most part
and luthor looks nothing like that greek actor he looks just like Dent without the hair