Shawn Michaels didn't get the nickname "Mr. WrestleMania" because of a winning streak like the Undertaker's -- he got it because of quality performances, plain and simple, many of which have actually been in a losing effort.
Looking at the WWE roster now (assuming Shawn is done, which I'd bet money he's not), who's the man to take over the mantra of "Mr. WrestleMania"?
John Cena has had many WrestleMania moments, but only a few great matches. Triple H is in a very similar boat. Chris Jericho has also had his share of moments, but year in and year out, he can be very hit or miss.
Now I know this one is going to hurt, fellow Internet fans, but the man on the post-Michaels WWE roster who has the best track record at Mania is a huge musclehead who probably isn't one of your favorites. But take a look at Big Dave's track record and you'll see that when it's Mania time, he can usually step up to the plate:
Mania 20: with Flair and Orton vs. Rock & Foley: Four-star match.
Mania 21: wins title from HHH. Four-star match.
Mania 22: Misses show due to injury.
Mania 23: loses title to Undertaker. Four-star match.
Mania 24: Fight Umaga in rare dud.
Mania 25: Misses show due to injury.
Mania 26: loses title to Cena. Four-star match.
Yes, he's missed two Manias due to injury (HBK and Taker have missed Manias because of injuries also), but he's had five Mania matches, four of which were four-star bouts. Try and find someone else right now with that track record.