No one worries about taking Hercules down? Herc's thrown down with Hulk, Thor and damn near every heavy weight out there.
Ares might not have Herc's strength, but he makes up for it in his lack of restaint and sheer experience. Gods have laughed off telepathy in the past and Petey can take on Ares, but he'd be a real under-dog in the fight.
Against the X-Men, I can see Ares being more effective than Gladiator or Juggernaut. He's far less restrained and far more ruthless than Glads and not as vulnerable to telepathy as Cain.
Who on their current roster can match him for power, really?