Two of the best in-ring performers in wrestling history.
Michaels was better at the high-flying stuff, and Hart was a better technical wrestler with superior ring psychology.
I prefer Bret's in-ring style from an entertainment aspect, so I give him the slight edge there.
Michaels was better on the microphone, although Bret had his moments (especially any time he was a heel).
Truth be told, both were better as heels in my opinion. Both had a natural cockiness that worked better as a heel wrestler.
This comparison is almost as close as it gets.
It is too bad their egos were so huge, or else they could have worked more together.
The only wrestler in the business with a bigger ego than Michaels or Hart is Hogan. Those 3, along with the Ultimate Warrior, are probably the Mouth Rushmore of wrestling egos.