Haven't gotten too far into Persona 3, so I can't speak for Junpei (I know he gets massively better later, but as of three months into the game, he's alright). But I love Ryuji. His social link is so good, it always feels contrived to me whenever he smurfs up; like he should be smarter, but the writers needed a comic relief moment. Yosuke feels like he always deserved anything bad that happened to him.

But yeah, the real answer is Eikichi Mishina aka glam rock Kazuma Kuwabara