98 was great.
06 is probably still my favourite. Really got me back into football and I was completely engrossed throughout. Zidane's revival/fall, Italy's redemption after their scandals, Ronaldo's wink, Argentina's amazing football with Riquelme, and many more, it was so damn good. Also felt like the end of an era for a lot of the great sides of the time - Italy, France, Germany, Brazil. All the big guns at their peak battling it out, the opposite of this world cup in a way which has been about the big sides (mostly) crashing out so far.
This one has definitely been special so far, though.