When you say better, do you mean that they performed better or were used/pushed better? Judging from your list, I'm guessing you mean that they were used/pushed better in WCW, as they were all world champions there but never really got higher than upper-midcard status in WWF. I'd add Ron Simmons to that list as well.
Pretty much all the names stated already. but if were going by accomplishments as well, then sid and Jeff Jarrett. Now I hated both these guys in WCW but they both were maineventers and world champions in WCW and sid got a lot more attention then in the WWF and he wasn't ment to be a transitional champion like he was in the WWF but then Russo came in to power at wcw.
Also I may be in the minority here but personally I liked booker t a lot more in WCW. In its dying days when booker was being pushed as a maineventer I loved his gimmick and the whole "don't hate the player, hate the game thing". I believe if WCW had held on and continued to exist he could have been A TOP face in the promotion. I think the WWF did more discredit him, even turning him into a joke for a while more then anything. When he did become world champion with the whole King booker thing, idk I found that gimmick extreamly tacky.
Definitely DDP. Started out as a solid mid-carder in WCW having some really entertaining bouts against the likes of Benoit & Eddie etc before moving on to become a three-time WCW Champion. Personally, I'd say one of the most over guys in professional wrestling in the late 90's. His first WWF storyline may have been with the Undertaker, but the whole stalker gimmick was a sham that he never truly was able to recover from. Had a decent spell as the European Champion in early '02, but definitely wasted in terms of talent.