Palpatine believed that one day, Lord Vader would be able to be more powerful that either himself or Yoda. So even the Sith Master did think that one day Anakin would defeat Sidious. The trouble for the Jedi was that in ROTS, it was not yet that time. Arrogant Anakin was powerful. Perhap the most powerful Jedi, and more so once he was tapping into the Dark Side. His problem was that he was overconfident, and in the end, the he was lead to a place of Obi-wan's choosing, for the final blow. Anakin and Obi-wan are about equally matched, but only because Obi-wan has practiced his defensive skills so much that he is THE Master of Defensive lightsaber combat. Even Master Windu acknowledges Obi-wan's mastery of this skill, and why they think Obi-wan should be the one to take on General Grievous. His defenses in a duel are basically impenetrable. Only Force powers can overwhelm him (as Dooku did), and against say , Sidious, Obi-wan would be outmatched by the Force powers. But with Anakin....Obi-wan knows how Anakin fights, so he can match him move for move for the entire battle. It isn't that Obi-wan is stronger, just skilled in just the right areas to eventually defeat Vader.
It is possible, that decades later, Obi-wan could have keep Darth Vader in a perpetual stalemate on the Death Star, but Vader was far more careful, so he wouldn't overextend himself to allow the old man to take him out like before. But what Obi-wan did at the end perplexed Vader, but used it anyway....just as Obi-wan planned.