I'd say its not possible to give them a solid ranking as all of them (except Mello, who's a step behind the others) have their strengths over the others in various ways. L is overall better at analysis than Light, but Light is better when it comes to tactics and using resources to his advantage. Near has the most composure out of the three and has more unconventional decisions to give him an edge, such as some that were barely legal. If having to give them a ranking, on an equal playing field, I'd say L ~ Light > Near >> Mello