My Pokemon were horribly underleveled, barring my Feraligatr. I only beat the E4 recently, and my Feraligatr did all of the work. It was saddening, to see my team of stars wrecked by Will's goddamn Xatu.
It took me around 5 tries to get through the Elite Four, mostly messing up on Will. My Pokemon were strong enough and type varied enough to beat the other 3 with ease, particularly Koga, but Will? All I had was Bite from my Crobat, Growlithe and Feraligatr, and sadly Psychic OHKOs the former 2. I beat them with mostly Feraligatr, Ampharos and for Bruno, my Crobat.
The Johto Elite Four were fun and varied really well in type, the only E4 that comes close to being like the Johto Elite Four has to be Unova's, but, well..who doesn't like Poison type ninja masters? I also like the whole Psychic/Poison/Fighting/Dark type line, as they all beat one another, except for Poison.