In all seriousness, for the most part, White wasn't much of a challenge to me. I had very few Game Overs (if I lose, I typically reset to give myself that feel) and most of them were against Ghestis. He really was difficult to beat. Nobody else in the game was. Many of the gym leaders were jokes and although I typically kept a consistent team, they really didn't have much of a problem with anyone.
I personally think that it was just as easy as any other Pokemon game, except playing through GSC for the first time. In my original Silver, I had a lot of trouble facing Bugsy's Scyther and Whitney's Miltank, but only because I was a newbie and didn't quite understand type advantages yet (and had started with Chikorita). I am replaying Crystal now. It's easy. Knowing those advantages and everything is what made Black and White seem too easy - GameFreak hasn't changed a thing, which sort of punishes those with knowledge. It doesn't press their boundaries and make them discover newness. It was the same game with different Pokemon. That is all it was.
BW was just as easy as all the others because they're all pretty much the same. GameFreak needs to give us something new, to tweak it (even in a minor way) every generation like Final Fantasy or Tales does with each and every game.
There's no doubt GF need to cater to the more experienced players in their games. I personally am hoping that BW and BW2 are just GameFreak testing the waters of more advanced story lines, and if that be the case due to the success I believe we will very soon get more challenging story lines and quests in future Pokemon games.
Back on-topic; I found myself having finding a type advantage before every gym in every game I've played, in Emerald for example I'd start with Treeko, catch a Wingull for second gym, get an Aron and Mudslap my way through third, I never struggled with Norman, Wingull again for Flannery, Aron dealt with Winona with ease, Tag team Tate and Liza with Treeko and Wingull, Treeko for Wallace and that's all 8.
Every gym leader in 3 Pokemon (Obviously I would have evolved at the first chance I got.)
There will always be something super-effective towards a gym before you face it.
As far as the Elite 4 goes...did you play the postgame and challenge them again? They're all level 70 and above. The first time you challenge them its meant to be easier so you can move along with the storyline. The second time is much harder.