I'd start with a lot of the classic TNA stuff, mostly because the last two years of TNA have been worthless in my opinion.
America's Most Want vs. Triple X- Steel Cage Match
This match took place in 2003 at a weekly PPV if my memory serves me correctly. Great match, fast pace, back and forth action, and a killer spot at the end of the match. Triple X vs. AMW is one of TNA's all time best feuds, makes me miss when TNA was all about having good teams in their company. I mean right now the only good team is Beer Money, considering LAX isn't a full time team anymore. But that's another subject. If you want good TNA action, check this one out first.
America's Most Wanted vs. Triple X- Six Sides of Steel match
One of, if not the last match these two teams had was one of the best. The stipulation in this match was that the loosing team had to disband. The above mentioned match was a better match, but this one was great as well. I don't want to give to much away, but lets just say, I've never seen someone walk the top of the cage, considering TNA's six sides of steel cages are so thin on top. Check out this match for sure.
Kurt vs. Samoa Joe Matches
Without fail the best of what I'll call "Modern" TNA feuds. Starting at Genesis 2006 in a normal one on one match, then at Final Resolution 2006 in an Iron Man Match, Turning Point and finally at Hard Justice. The first three were probably the best of them all. Pitting two of the best wrestlers in the game right now against each other with no gimmicks, just wrestling, which is rare in TNA, but beautiful when it happens. Not much more to add, these are just great matches.
Abyss vs. AJ Styles Six Sides of Steel
Lockdown 2005. Really good match. AJ styles face past style vs. Abyss' hardcore style. There is good use of tacks in this match that could make anyone cringe, some stiff shots from the cage door, and some nice spots.
Against All Odds 2005
30-Minute Ironman Match- X-Division Title
AJ Styles(c) VS Christopher Daniels
Best Iron man match ever period. It's extremely fast paced. The match is incredible and the ending is absoultely great. I'm not gonna get into too much detail because I don't wanna spoil it.
AJ Styles vs. Samoa Joe- X-Division title match
Great stuff here, one of Joe's early matches in TNA, during one of his first real TNA feuds against AJ Styles and Christopher Daniels. This took place at Turning Point 05 (?). There are some good high flying moves from Styles, nothing absoultely crazy about this match, but it is an enjoyable match put on by two of the best home grown TNA talent.
AJ Styles
vs Christopher Daniels vs Samoa Joe from unbreakable 2005.
This match symbolizes everything TNA was at its best, as i dont personally like their new product so much. It showcased two of the guys in daniels and styles that put tna on theri backs and carried it through much of the early years.
Its fast paced, high flying, and yet a very technical display.
I dont think its even up for debate, this is the greatest match tna has ever had. Bar none.
LAX vs. AJ Styles and Christopher Daniels- NWA Tag team title match
I'll go out and say it, the last good Tag team title match in TNA. It happened at the 2006 Bound for Glory event. It took match of the year for that year, so you know it's good. Two great teams going at it with no holds barred. Good spots from AJ and Daniels as well as LAX. Just a great match overall.
I could go on and on and on, but there isn't enough time. I suggest going to your local video store and buy these DVD's.
Best of the X-Division Volume 1
Best of the X-Division Volume 2
50 Greatest Moments in TNA history
Best of Abyss
Phenomenal: The Best of AJ Styles
Phenomenal: The Best of AJ Styles Volume 2
Best of the Bloodiest Brawls Volume one and two
History of TNA Year one
Those will show you pretty much everything you missed.