Lets clear some things up...
Im surprised how many posters here in this thread seem to have no idea on how Brett's first World Title win came about. SummerSlam was written to set up a big feud between Ric Flair & Ultimate Warrior, which immediately commensed on the US house show circuit and WWE TV. It seemed (but was never confirmed) that Warrior vs Flair was destined to main event Survivor Series, likely with UW winning (Vince definately preferred strong hero characters as champ). In Phoenix Flair was injured during a press slam spot with UW, breaking bones in his ear which caused him equilibrium problems. No one knew how long it would take to clear up but niether Flair nor Vince believed he could continue wrestling so Vince decided to switch champs ASAP, not wanting to lose revenue on the circuit by having a champ who didnt wrestle and risk the fact Flair might not be better by S-Series. Hart was chosen because A) He was very popular & well established with the audience. B) He could be relied on to work a full time schedule on the touring circuit (Hogan never worked full time on tour, sometimes going over a month without a match, but Vince made Savage & Flair work full time schedules as champ, which seemed important with the industry in general seeing declining ratings and attendance for 3 straight years after a peak in 1989). C) Hart wasnt a trouble maker, he was viewed as a comany man.
That last part was important because Warrior and WWE were never fully on good terms after his contract dispute and long absence the previous year. UW's lackluster performances during his 92 comeback didnt help, injuring Flair being about the last straw.
UW disapeared from TV when Hart won the title, with no explanation (Flair was gone over a month too, but his absence was explained on TV as related to injuries he suffered in his title loss to Brett). UW returned to TV briefly when Flair did, ostensibly to finish their feud at S-Series but UW disapeared right after his return after a TV segment on Saturday Night's Main Event in which Flair punked him with help from Scott Hall aka Razor Ramoan. This lead to the Curt Henning comes out of retirement angle but it seemed to indicate how far UW had fallen since S-Slam. This is why Brett's first title win had no build up and seemed out of nowhere.
Flair & Hart in a joint interview discussed the whole situation last year, with Hart admitting he was surprised when Vince told him the news (in his words he thought he was summoned to Vince's office to be reprimanded for issues he had with his passport that caused him travel delays).
As for Hart's legacy as a performer, he's a bona fide Hall of Fame talent, he was great in The Hart Foundation tag team as WWE's answer to the Midnight Express, his initial singles push which included a memorable IC Title run and great matches with Henning & Roddy Piper was a significant success, and he dominated the WWE Title scene 1992-97 which is no small accomplishment. There were highlights in WCW too, matches with Flair, Sting, Lex Luger and Chris Benoit that just add to his legacy.
Do I personally rank Hart at the top all time ? I do not based on his charisma, his character simply wasnt as entertaining as Austin, Flair, Hogan, etc. I think Hart gets unfairly criticized for his "lack of charisma", he wasnt "Dean Malenko Boring" so to speak, and he was effective at getting over with audiences as both a heel (especially in 96 & 97) & face (unlike Sting, who never was a good heel or Ricky Steamboat who never even worked heel), he just comes up a bit short in entertainment value compared to a lot of others. If he was truly as dull as some call him he never would have had the success he had.
As far as Hart's character, that is a complicated issue. Was he more upset at the turn away from "Disney Style" programming during the start of The Attitude Era or was it that HBK was supplanting him as the company's top star (and the fact HBK by his own admission was total *&%$# and not a "company guy"). How much of Hart's vitriol in interviews in the last 16 years is related to the negative way he let go from WWE, his mistreatment by Bischoff in WCW, and the injury that prematurely ended his career, denying him the "last run" Hogan had or the great ending storylines and matches HBK & Flair recieved in the latter days ? Plus, shouldnt those who criticize Hart's alleged negativity give him credit for burying the hatchet, making peace, and publicly praising Flair, HBK, & Vince in more recent years ?
I think Hart is comparable to John Cena, essentially Cena is the modern era Brett Hart, a guy who reached major heights of success during "down periods" in the industry. Also, like Cena, Hart was a work horse for years, on TV, the house show circuit, and PPV, also doing commercials, TV appearances, and charity work helping to promote the company. It isnt their fault that their ascension to "SuperStar" status happened when the industry as a whole was declining after an epic peak, in fact in one way that makes their success more praiseworthy, hitting comparable heights to many of the business' biggest legends during an era with lower numbers than when those legends reached their peak.
In another way Hart is comparable to 90s era Flair. Wether it was an attempt to spark ratings or maybe a response to his "lack of charisma" but it seemed as if Vince & WWE were always looking to replace Hart as the #1 guy, yet they always came back to him, time & again, because A) Different attempts to crown a new top guy (like Nash & HBK) didnt deliver the change in business Vince sought B) Vince & WWE always knew Hart would deliver good numbers, even in down times, maybe they wanted "better numbers" but when others didnt deliver WWE knew consistently what they could get from Brett . In WCW it was same with Flair....Vader not delivering what they wanted, time to change, Go To Flair. Sting not delivering the numbers they want, Go Back To Flair, Hogan not drawing enough vs Beefcake & Vader, bring back Flair. With Flair it was more an age issue than entertainment value (he was in his mid 40s when he returned from WWE, still viable in the ring and valuable with the audience, but too old to be a long term answer). In the end, Flair always propped up the numbers and kept things in good stead while they searched for the next big thing.
Its not an easy situation to be in, but Hart always worked his *** off and tried hard to deliver for the company.
He's one of the best, if he was a quarterback he would be say a Brett Favre or Troy Aikman, a legit Hall of Fame talent and definately great, but not quite Joe Montana, Johnny Unitas, Tom Brady great. That's nothing to be ashamed of, in fact compared to the overwhelming majority of others who have done that job it's significantly better.