I think the Quality of the two sides probably shades the 99 semi for me. There were multiple ATGs on both sides in the 99 semi final.
2019, to be honest, wasn't that exciting or interesting in the first half. It was a slow burner. The finish though was the greatest of all-time but it can't match the big match moments of the 99 game. Also in 99, SA and Australia were the best ODI teams in the world so it was much better backdrop.
99 was just a better quality game from the 1st over when Pollock took Mark Waugh till the end, and it kept swinging one way to the other.
Australia were comfortable at 54-1 and then Donald storms in with 2 wickets in a over.
Then Australia were 4 down and Waugh and Bevan rebuilded.
Pollock crashed through but Bevan got them over 200 before Donald yorked Australia so they couldnt score too many.
SA got over to a solid start and then Warne magnificently pegged them back.
SA rebuilded slowly and by the 40th over you didn't have an idea who would win. The last 6 overs, the game was literally switching to each team's favor ball by ball, Klusener would smack it and then they would take wickets from the other end. Reiffel's dropped catches, those two awesome fours at the end, missed runout and then the final tragedy.
Probably the greatest cricket game ever, not just ODIs.