Well they've only been around 8 and a half years, and unfortunately they plateaued in 2006. So I think the list should be kept small, just for people that either made a legacy in TNA, or helped take it to truly a new level.
1. AJ Styles - The obvious choice. The face of TNA since day ONE! Not only was he the first Triple Crown Champion, he did it 3 times over before anyone else could even get it once. Yes the 1st (and at this point) only Grand Slam Champion. I sometimes like to joke that he'll be the only man to ever hold all of TNA's titles, being the only man to hold The Legends, Global, and Television title in that belts short existence. And let's not forget that he, for at least 1 year, had the undeniable proof of being the best wrestler in the world when he won the poll over such guys as John Cena, CM Punk, and Chris Jericho. He's the first guy in TNA to take that honor. If TNA never has a hall of fame, and even if they eventually fold.. AJ is one of only 2 guys I think that should qualify for the WWE HOF, based of his accomplishments in wrestling, and where he was able to take TNA. I mean they already have a list full of guys who never accomplished jack in a WWE ring, and AJ Styles could make a great contribution to that list.
2. Jeff Jarrett - Some might disagree with Jarrett being in, but bottom line is, without him there would be no TNA. He's the other guy on this list that I would say could claim a spot in the WWE HOF based off his accomplishments in TNA alone. Not to mention his accomplishments before hand in WWE and WCW, in TNA he added 6 reigns as NWA World Heavyweight Champion to his resume. And while the circumstances of how he got so many reigns may be questioned, it really worked. Everyone knew he ran the place. So he makes himself 6 time champion that dominates the title picture as the top heel for 4 years. It helped get guys like AJ Styles over in the main event, and made the Raven's and Christian Cage's bigger and even more over just by walking in and wanting the title, because they immediately became savior's that the fans lived through. Love it or hate it, he's earned his spot.
3. Raven - As previously stated, the first real big name to make the jump over to TNA. It was perfect timing, and he was honestly the perfect person. I think they may have missed the opportunity to really make him a main stay in the main event. If he could have beat Jarrett for the strap back in the Asylum days, I think he really would have just had everyone eating out of the palm of his hands. He's continued to make contributions to the company as recently as this past year with EV 2.0. Though I think again they missed opportunities to have him maybe work in creative, an agent, or at the very least, a manager.. he still found ways to help. Remember Serotonin? If it wasn't for Kaz being in, then eventually breaking away from that stable, who knows where he would have ended up. Raven, TNA HOF? Yes.
4. Sting - Not much of a case has to made for Sting to be in any wrestling HOF. But him choosing TNA over WWE always made him feel like TNA's only legend. Sure he will probably always be remembered as a NWA/WCW guy.. but the work he's done in the greater part of the last decade for TNA is something that I think will make his legacy that much greater.
5. Christian Cage - I originally didn't have Christian on this list. But after thinking about the impact (no pun intended) he had on TNA, and really how huge it was.. I couldn't over look him. Not only was his initial impact huge, it never lost momentum during his TNA run. He was the biggest signing since Raven, but the real first big name to actually JUMP SHIP and choose TNA over WWE. For a brief period of time I had stopped watching TNA due to it's uncooperative schedule on Friday afternoons, then Saturday nights. But once I heard Christian had showed up, I made myself find time for TNA again.. and I haven't stopped since. If that isn't a major impact, I don't know what is. Then add in two World Title reigns, including a savior like victory over Jeff Jarrett for his first title. Also add an undefeated streak that lasted 2 years, the lasting effect of the Christian Coalition stable that really helped AJ evolve to the next level, and all the GREAT matches he had, and really.. Christian Cage is a no brainer for TNA HOF.
6. Kurt Angle - You had Raven, you had Cage, then you had Kurt Freakin Angle. The signing that shocked the world! And no matter what they say on TNA TV, Kurt Angle is in fact, the biggest signing in the history of TNA wrestling. More so then Sting, Christian, Foley, Hardy, or even RVD (it just took em too long get him). Just like Christian, he brought a new wave of exposure, interest, and attention to TNA that the company had never seen before. His feud with Samoa Joe is still to this day my favorite feud in the history of TNA. When he came in and became the first man to beat Joe, I knew it would only be a matter of time before he took the company over. He then went on to become the FIRST TNA World Heavyweight Champion and the company's 2nd Triple Crown champion. I still say Bound for Glory 2007, from top to bottom, is the best BFG ever, and that was headlined by the well built Angle vs Sting. He was creator of the Main Event Mafia, a group and storyline that dominated TNA for a YEAR! Not only has he benefited TNA with his star power and amazing matches with the likes of Joe, AJ, Christian, Desmond Wolfe, etc.. the way he's helped the company recruit and grow is something they should really pay him for. He's promised to stay with TNA till he retires and even beyond that, and if that's true, then I think signing Kurt Angle will turn out to be the smartest and most beneficial move the company ever made.
And that would be my strict list. I'd love to add others like Daniels, Joe, and even Borash. And cases could possibly be made for the likes of Abyss, Killings, Jerry Lynn, and America's Most Wanted. But only the 6 above made the necessary impact and left enough of a legacy that in the world of pro wrestling, will always be remembered.
