Bret Hart matches Shawn for in ring work but HBK was a better mic worker.
If Shawn Michaels had never come back in mid 2002 then his and Bret Hart's singles career in WWE would have been around the same time frame and of the same level for their in ring work but Shawn Michaels did come back and then added another eight years of great in ring performances on top of the first seven. This thread is WWE related so anything that Bret Hart did in WCW is not included although he didn't really have that much too remember from WCW outside of the feud with Sting.
When Shawn Michaels returned at SummerSlam in 2002 he somehow managed to have the best match of the year as far as in ring work was concerned despite not wrestling for four and a half years and then followed that up with The Elimination Chamber and Three Stages of Hell match with Triple H again. Look at 2003 and the feud with Chris Jericho and their matches especially WrestleMania 19 or in 2004 with his three way feud and matches with Triple H and Chris Benoit or the singles matches he had with those men as well.
In 2005 he was unbelievable and produced great matches with Edge and Kurt Angle on more than one occasion not too mention he carried Hulk Hogan's sorry ass to what was probably one of Hulk Hogan's greatest matches as far as in ring work was concerned. In 2006 he managed to get what was voted as the Match of the Year by PWI from Vince McMahon who was a 62 year old man who isn't even a wrestler and then went on to good matches later on in the year with the combination of Randy Orton and Edge in the D-Generation X/Rated RKO feud.
In 2007 which was a year he had to take some time off for a knee injury he managed to have great matches at the start of the year with Edge and Randy Orton before producing arguably the two best matches of the year against John Cena at WrestleMania 23 and then the rematch on Raw in London. 2008 we saw Shawn Michaels and Ric Flair at WrestleMania 24 but the feud after against Batista produced two of the best matches of Batista's entire career, the feud after that with Chris Jericho was the best of the year by far and produced the best matches of that year also.
Obviously in 2009 we saw THAT match with The Undertaker at WrestleMania 25 but we also saw some good matches with JBL at the start of the year as well against John Cena again, later on that year Shawn Michaels was involved with what are to this current day the best matches that Cody Rhodes and Ted DiBiase have been involved in. The going into 2010 we saw the restarted feud between Shawn Michaels and The Undertaker which saw the great Career vs Streak match at WrestleMania 26 which was the best match of last year by far.
Since returning in 2002 Shawn Michaels has won every Match of the Year by PWI since 2004 and should have won it in 2002 for the match against Triple H at SummerSlam but Rock/Hogan did because of how big it was rather than how good it was. In 2003 again he could have won it for his match against Chris Jericho at WrestleMania 19 but it was basically a coin toss between that and Kurt Angle/Brock Lesnar in their Iron Man match on SmackDown which did win but there was nothing really between the two matches and either could have won.
To win Match of the Year every year since 2004 and have matches that could very easily have won in the two years that he didn't show just what Shawn Michaels has managed to do since his return and that is why as far as being an in ring performer in WWE goes he is above Bret Hart because Shawn Michaels came back to add to what he had already done. Bret Hart on the other hand unfortunately could not because of his stroke and concussions added to the fact his relationship with Vince McMahon was null and void at that time, to do what Shawn Michaels has done for an overall total of fifteen years and have the matches and performances that he has puts him above everyone else as far as WWE is concerned which is something that a HUGE amount of people inside WWE and in the industry have also said.