He would've been where Jarrett was.
I don't think he would've been a main eventer all the time like Austin, Taker or Rock. But, they even planned to put Jarrett in the main event against Austin in a program, but Austin turned it down. Jarrett not getting his planned program with Austin is why he jumped to WCW.I'm gonna agree with @The Valeyard and say Shane would've been Jeff Jarrett level if he had somehow stayed nice with The Clique and stayed with WWF in the Attitude Era. Maybe a few Intercontinental Title and European Title runs but that's it.
Being a big fish in a small pond was best thing that ever happened to Shane Douglas so people could believe that he was held down by guys that were actually way better than him.
Did I mention I hate Shane Douglas?