Palpatine groomed Anakin for 13 years, from when he first met him on Naboo to the final moments of Anakin and the birth of Vader. He cleverly guided Anakin in the directions Palpatine wanted him to go and manipulated situations and events around him so he could make him his new apprentice (poor Dooku...)
Now, we know that in Darth Vader (in the suit) Palpatine did not get the Sith apprentice he was hoping for. Vader in the original trilogy is nowhere near as powerful as Darth Vader pre-Mustafar (although the fearsome appearance of the suit instills so much fear he more than compensates). Anakin is the most powerful Jedi of them all, and without his terrible injuries he would have been even more powerful and dominant, likely taking Palpatine out and ruling himself. But we know all this, it's in the films.
But, a second question.
Perhaps that wasn't a bad thing for Palpatine. His fights with Mace (which took a huge toll on him) and Yoda must have taken something out of Palpatine too. Perhaps the Emperor we know from the original trilogy isn't as powerful as he might have been.
Both Anakin and Palpatine are physically scarred in terrible ways. The Emperor basically locks himself away and has Vader conduct his business for him under Tarkin. And Anakin - in many ways, as much to the general public as to himself, Anakin is dead. Annie wasn't only physically scarred but mentally and emotionally as well, and it takes Luke's love to bring the truth and the realisation that he is the Chosen One back to him.
(Doesn't Sith make the end of Jedi SO much more powerful now?)
So, in summary - while we all accept that Vader was diminished by his fight with Obi-Wan, perhaps Palpatine was also by his two battles with Mace and Yoda.