Honestly, the answer to such a question depends on multiple factors. Do you mean which class has the most potential for damage? Do you mean which one can level the fastest? How about do the best in PvP? PvM? Take out bosses (discounting guardians)? Overcome resistances? Dig the best?
See where I'm going with this?
Every character class performs differently in different situations. Generally speaking, powers do more damage with a physical hit. Throw in skills and Bunnies excel at single target damage while Buffaloes branch out and do theoretically smaller (yet generally still pretty high) damage to multiple targets. Magic types have AoEs but traditionally do a bit lower damage, while at the same time relying on elements. This helps in some cases, hurts in others. Depending on the path one takes, different focuses become apparent. The same type of analysis can be done on Charms and Sense types, but I'm not too familiar with them so I won't try to pretend I can generalize about them properly.
As someone already mentioned, MyShop, or more realistically just equipment in general, makes a huge difference. A Buffalo with level 125 ultimate sword, helmet, and shield is still going to do less damage than one with an element attribute comped Golden Sword and Golden Lion Shield on a base melee attack. Just like someone with a Yoba Pouch and Azhi ring for accessories comped for MA is going to do more damage than someone with their guardian and say, the Rainbow Necklace comped for MA.
So to be perfectly fair, while some classes may excel at some things better than others, you have to kind of clarify in what regard you're looking at the class before you can say whether or not it's better than another. I say better because that seems to be more what you're saying: "X class is better than Y class" for whatever situation you're using to define the usefulness of a given character class.