If Undertaker had been in WCW then I doubt we would have seen a Starrcade counterpart of the streak. First of all, he would have had to remain as dominant over there as he was in WWE as The Undertaker. That would have been much more difficult to do under a different gimmick and with guys like Hogan abusing their creative control. Secondly, WCW would have to last long enough for the streak to reach 20-0.
There are a number of potential matches that could have been great to see. Sting being the obvious one, over in WCW he could have faced both the classic and crow versions of Sting. Nash, Hogan, and Goldberg would all have been interesting as well. We all know how Goldberg's streak ended though, and with Taker I am certain that something similar would likely have happened. He would have been fed to the nWo before the streak could reach its full potential, and none of them would need the rub received from ending it.
There are a number of potential matches that could have been great to see. Sting being the obvious one, over in WCW he could have faced both the classic and crow versions of Sting. Nash, Hogan, and Goldberg would all have been interesting as well. We all know how Goldberg's streak ended though, and with Taker I am certain that something similar would likely have happened. He would have been fed to the nWo before the streak could reach its full potential, and none of them would need the rub received from ending it.