I have to agree, the 1998-2001 era of "Sesame Street" was pretty good. Sure, this is when they introduced "Elmo's World," but we still had the classic "magazine"-esque format, and it heavily emphasized the classic songs and featured the classic characters, probably to celebrate the show's 30th season. Season 30 was also the first season in a long time with no rerun street stories, which explains why the number of episodes was reduced from 130 to 65 (they couldn't rerun any previous episode street stories anymore due to the introduction of "Elmo's World.") And yep, the 1998-2001 opening sequence was a nice throwback to the classic intro sequences; again, probably as a deliberate homage for the show's 30th season. Interestingly, they still continued to use the 1992 "Dancing City" closing credits, and the calypso-esque "street scene opening" music, maybe because they figured "We've already changed the show so much for this season, so let's leave a little of the modern stuff in for the returning viewers." At least the credits still seemed to fit with the 1998-2001 era, but a couple of years after that, it was seriously dated.
A few recurring classic sketches began to appear less and less during that time, though. Only a handful of 1998-2001 episodes had any Kermit News Flash segments in them, and Season 30 was the final season to feature any new "Monsterpiece Theater" segments. (An interesting note was one Season 30 episode actually showed the "39 Stairs" segment with the full 1992 "Library" intro instead of that simple "green curtain" intro; it was probably an editing mistake or something.)