1, Dynamite Kid, I still believe skill wise he's the greatest wrestler of all time and was way ahead of his time especially his japan work, From what ive heard he didn't sound like the nicest guy backstage but his matches I think was in a whole different league to anyone who came before or after never really got the singles career he deserved.
2, Chris Adams who rarely gets any mention and was in one of my favourite feuds of all time against Steve Austin I think his work was consistantly good and could have been a great addition to the WWF during his time.
3, Fabulous Freebirds, My favourite tag team of all time and surprised their still not in the hall of fame, As great as the original 3 freebirds Hayes, Gordy and Roberts were I also think the newer incarnation of the team Michael Hayes and Jimmy Garvin gets overlooked sometimes as they were one of my favourite to watch in early WCW.
4, Sabu, was such and innovative guy would have been so cool seeing him feud with some of the bigger name wrestlers of the 90s such as The Hitman, HBK, Undetaker or Sting for example, I thought his WCW run ended way too early and was a nice touch adding The Sheik as his manager by the time he did reach WWE his body had been so beat up his best days were long behind him.
5, Jerry Lynn, did relatively nothing in his only short WWE run which was such a wasted moment as he had so much talent.
6, La Parka, one of the biggest name luchadore wrestlers to never make it to the WWE, Skill wise he may not have matched up to other luchadores but entertainment value in his matches he was at the top.
7, Million Dollar Man Ted Dibiase, Its difficult to call him underrated when he was such a huge star during his era but I still think he never reached his full potential and should have had at least a couple of world title runs and should have been WWE's top heel at the time equal of the level Ric Flair was to the NWA.
8, Marty Janetty, His return after the Rockers split seemed huge at the time but he had not even gotten his revenge match at Wrestlemania against HBK and by the time Summerslam came round he jobbed in a squash match to Ludvig Broga then just faded away, I'm not saying he deserved equal success to HBK but did deserve at least more of a decent run as a singles wrestler.
9, Ultimo Dragon, Think he should have stuck around the WWE longer theres so many great matches he could have had which never happened.
10, William Regal, Never really achieved the main event level that he should have, Debuted in WWE with a ridiculous real man's man gimmick would loved to have seen him debut instead going straight after the world champion Steve Austin.
I didn't include who I thought on the current roster like Luke Harper, Cesaro or Damian Sandow as I think they still have a chance to excel.