Whilst I am not disagreeing per se, Anakin would only be the most powerful in the force.
If Obi-Wan had not capitalised on Anakin's mistake, I get the feeling that a person of his nature would become an accident waiting to happen. He may have calmed down, but he may have become even more reckless!
This is why I think that people concentrate too much on raw force power.
I would actually take Sidious over a maxed-out ("potential" wise) Anakin.
Light_Sith has a good point. You can be a master swordsman or powerful with the force, but if your head is all over the place, you cant use them effectively.
I would say, a full potential Anakin, is Anakin reaching his maximum level in both force mastery, swordsmanship AND mentally. If he had been taught by Qui-Gon Jin or Yoda...I feel his temper would have been calmed. I think that a focued, non-aggressive Anakin at full power, would beat Sidious. I think if Anakin isnt focued, then Sidious' mind games might rattle Anakin and eventually give Sidious the chance for victory.
Anakin is extremly skilled. He would not only be much than everyone but more skilled as well. Look he was a Jedi Knight in Rots. At the level of Knight his power in the force and skills with the lighsaber were far above any jedi in history. At the age of 21 he was alrealy approaching Mace Windu in skill and power. Obi-wan was still a padawan at the age of 25 by 25 Anakin would have been the strongest Jedi in the order.