Qui Gon, Obi Wan was too much of a Puritan to connect with Anakin as a Master. Their relationship was more brotherly than anything else. Qui Gon would have been able to connect to Anakin with his unorthodox training style.

Qui-Gon, he understood Anakin and most important, Anakin respected him and saw him as his father. Obi-Wan is a good master, but not the best for Anakin, Anakin saw Obi-Wan as a brother or even as a little brother. That's not how a master pupil relationship works. Qui-Gon would have been the best choice.

Maybe Mace Windu would have been a good choice. He seems to be the one who frustrated Anakin more than anyone else. Maybe if they were forced together they would get used to each other and mellow at each others personalities. Also, didn't young Mace have trouble keeping his temper in check? Maybe that's just the person who Anakin needed to learn to control his emotions

I chose Plo because of his compassion towards people and Anakin would've gotten the help he needed through that compassion.

Qui-Gon was like a fatherly figure to Anakin, so he would've been a suitable master for Anakin. I'm not saying Obi-Wan was bad as a master, but he treated Anakin like a brother, which wasn't what Anakin needed, what Anakin needed was a father.

My first thought went to Qui-Gon and Mace. The former had unwavering faith in Anakin, that could've helped him integrate into the Jedi Order. And he seemed to have done a good job with Obi-Wan, so, he would'have probably been a good master to Anakin as well.

But I can't help but wonder if Mace, too, could've helped Anakin steer away from his dark path. These two distrusted each other in Canon but maybe they would've had more of a chance to get to know each other better and trust each other if they had a direct master-apprentice-relationship. I've also heard of Mace that he had trouble himself to control emotions like anger when he was younger. So, I think it's possible that he would've noticed Anakin's decline to the dark side in time and would've been able to help him deal with that, based on his own experiences. Of course, there is also the possibility of these two clashing with each other. But then again, Anakin and Obi-Wan had arguments from time to time as well; doesn't seem unusual for a more stubborn, rebellious teenager like Anakin was. But I like to think these two would've gained more respect for and trust towards each other if they had spent more time together and had a more intimate relationship. After all, there aren't all that many differences between them.

So, my choice would be Mace although I also think Plo, Yoda, and Qui-Gon could have made great masters to Anakin, too (not counting Obi-Wan since we're talking about alternate possible scenarios here)

Judging by this poll people are going with if a certain Jedi Master wasn't run through by a certain Sith Apprentice.

Qui-Gon should finish what he started.

Mace purely for the interactions they would have.

Qui-Gon or Mace

It has a hinted at answer with the name of the song in the maul fight "duel of the fates" which is meant to represent that if qui gon lives than anakin will not fall to the dark side