I think Blue is the only real challenge among the Kanto Gym leaders. If you don't OHKO Exeggutor and it uses Trick Room, you'll be at a severe disadvantage because it's likely his Pokemon will be slower.
I mean, I love how Johto and Kanto (okay, mostly Johto) look in Gen 4. And there's lots of daily/weekly tasks to do in the post-game. But it's so damn painful and annoying just to complete the damn game, and the lack of a VS Seeker doesn't help at all.
Don't ever bring this up publicly on the forums though, or you'll be marauded by nostalgia freaks.