I feel like I've seen this thread before...
Well, first off, the terms for the battle are pretty vague, and by vague, I mean non-existent. Comic Vine has a pretty good thing on this.
http://www.comicvine.com/forums/batt...tion/675391/#1
Quote from their forum rules, "Be Specific About Fights
I think this is probably the most important rule, and when it’s followed, many other problems go away. When starting a battle you need to be specific about how everything is going to go down. This includes a lot of factors. A lot of posters just type "fighter 1 vs fighter 2, who wins?" and they're done. Putting just a little effort into it can sort out a lot of questions that pop up later. You can determine if the characters involved are acting in character (like they normally would as their personalities dictate), if they are “bloodlusted” or anywhere in between, how much time they get before the fight (prep), where they're fighting, what gear they have with them, which incarnation of the character, any power limitations, etc, etc. It really isn’t hard to flesh out the battle a little and it goes a long way.
Writing some options again to make sure they’re easy to see:
In Character or Bloodlusted
Prep Time or No Prep Time
Setting (time, location, bystanders, available resources, etc)
Gear (standard weaponry/gadgets/items, unarmed, special weapons)
Character Version (current version, original, alternate universe, etc)
Extra Rules (time limits, boundaries, what counts as win)
When these things are left out it’s generally assumed that characters are fighting to the best of their ability but still within the limits of their personality, using their standard gear, have no prep time, and are their current versions. Their starting distance is close and the setting is most often a city. Without any specifications to a battle, those are what we go by. It’s always best to give as much information about the fight in the first post."
Lacking any kind of rules or context, I say that Goku wins on the basis of being faster than light. There is in fact a speed of thought, (electricity) and since electricity is just below the speed of light, Goku can act before Metwo can think to utilize any psychic powers against him. If Goku were out to kill Mewtwo, I believe he'd punch him into non-existence before Mewtwo could even register what happened.
Even if Goku were to die, he does have the pretty retarded advantage of being able to teleport across dimensions and attack people as a soul, like he did against Bojack.