Unlike what a couple of people have said, I liked the concept of the Elite Four members forming a ladder rather than a group of equals. With each trainer you beat, it felt like you moved up another step on that ladder, one step closer to becoming the champion. For example, in Red, I always got the impression that Lance was clearly at the top of the heap compared with the other Elite Four members (particularly thanks to his role as Champion in Gold). If he had been knocked down to the same level of the other Elite Four members just because your rival beat him, that wouldn't have made much sense to me. I guess the plots are designed to make the different members seem more equal now, so I suppose the shift makes sense, but I still liked moving from easier to more difficult opponents as I progressed through the Elite Four.
Also, assuming your Pokémon aren't terribly overleveled (which they're likely to be in the newest installment, but still), each encounter becomes more challenging than the last because the levels of your opponents increase (assuming your levels don't increase more quickly than their levels do). By contrast, if you level up throughout the Elite Four, and all of them have Pokémon at the same level, it should become easier for you to progress over time because you become relatively more powerful (not considering type advantage differences/assuming you have enough variety in your team to tackle any Elite Four member).
I would agree that the more pressing issue is the smaller size of the Elite Four rosters, though. They should really have at least five Pokémon (like the older games). Perhaps cutting down to four Pokémon is designed to make things easier for younger players, but most of us handled the larger rosters just fine when we were younger, so I don't see why kids today can't as well. (Wow, I'm starting to sound like one of those people who goes on and on about "when I was younger...")