IMO every match between HHH and HBK fought on ppv was at least 4 stars. I think there are two main reasons why the OP was previously unaware of this match and is wondering why people "dont talk about" this match.
1. It's a big name matchup contested at a small-name ppv - Just think about Austin/Rock. Everyone knows and generally remembers each of the three battles they had at WrestleMania but what about the stellar match they put on at Backlash '99? With feuds that have so many ppv contests between them, the smaller names seem to get lost in the shuffle unless they are significantly better than the other matches in the feud (such as Taker/HBK at Bad Blood '97 or Cena/Punk MitB '11). Hunter and Shawn put on a flawless performance at Bad Blood 2004 but does it really stand out over their 5-star classic at SummerSlam 2002, the double countout finish at Royal Rumble 2004, or the main event of WrestleMania XX?
2. The IWC has such little respect for the in-ring career of Paul Levesque - Thank god he was able to produce a wrestling show that appealed to this demographic, because without it he'd still be mercilessly slandered by an overwhelming majority of the posters on this site. Whether they feel he rode Shawn Michaels, Stephanie McMahon, or Vince himself for his spot everyone seems to unfairly assume that HHH is the last person responsible for his own success. As a result, a lot of his brightest moments are dimmed by the dismissal of bitter fans who say he slept his way to the top. Sure, WWE propaganda helps us remember some of the keys but he's had a lot of memorable matches and moments in WWE history. A lot of his best matches are then forgotten, I put this match on a list with his HiaC classic vs Foley at Nay Way Out 2000, his LMS match vs Jericho at Fully Loaded 2000, and his 3 Stages of Hell match vs Austin at No Way Out 2001. All extremely good matches, but seem to get overlooked simply because HHH is somehow unqualified as a performer in the eyes of the average fan.
I hope my rambling was useful in some way shape or form. It's a great match I'm glad you enjoyed it