It has to be Austin. He took the torch from HBK at mania 14, and had a great run as champion vs a stable of guys around McMahon, and then a nice program with Taker. SCSA even put over Kane as a main evener, if only for a night.This whole year was Austin at his peak, the crowd was over for him, and then he dropped down in the card to let Rock and Mick get over. If the MVP for this period was anyone else, it could only be Mick, if only for his versatility alone.
I have to say, I think that the Rock/Foley program from the end of 98 through Wrestlemania was better than anything Austin did with another wrestler. All of Austins best moments were always with Vince. Anyway, after seeing Russo's post about how the main event was meant to be Austin-Rock-Foley three way makes so much more sense thinking back on the build. When Mick got shoehorned into the ME at wrestle mania 2000 the next year, it felt forced and overdone. Remember he was gonna come back and wrestle one last match, then retire on raw and vacate the title the next night, linda mcmahon tryna sell that crap get out of my face. Anyway, they should have had the three way at XV15 (Rock Austin Foley), and Hunter V Rock at 2000. But as always, I'm sure politics got in the way. Same thing happened at wrestle mania 29, go back and look at their booking of Punk, he should have been in a three way with Rock Cena Austin instead of Rock Cena 2 which nobody cared about. People would have watched Rock wrestle the mop as Hunter would say, he's just that money (see; Raw, Rusev which is otherwise campy garbage). Rock could have MADE Punk. Not like he's over not, but MADE to look legit on the same level with THE ROCK, WWF legend and the highest paid action star in Hollywood? Well, I guess a man can dream.
Not sure why everyone gets on triple threat matches, they can make everybody look strong, protect the stars by lowering the work rate, and are faster paced main events for the fans. See the ME's of 24, 25 and 30 as good examples of that.
TL,DR: Stone Colds the Mvp, and thats the bottom line- with Mick a relative second bang bang