Alright, let's be as fair and unbiased as possible. Let's put our own opinions and feelings aside a genuinely analyze the combatants.
Sonic and Mario are virtually equals in many aspects:
-They both can jump high.
-They both are athletic.
-They both have an undisclosed amount of super strength (though Mario's best feats in this category are limited to throwaway gag cut-scenes)/striking power.
-They both like to jump into battle and ask questions later.
-They both win fights where they are the under dog.
As far as their base physical abilities go, we basically have two super athletic warriors that are virtually equals. Now consider that one of them just so happens to be able to move faster than the speed of sound. It's really no contest here.
When it comes to power-ups, Mario has a quantitative (larger number) advantage over Sonic.