The same theory could apply to Gen IV which gave us such abominations at Rhyperior, Magmortar, and Magnezone who were made to be "Top-of-the-game" Pokemon, and yet, they were pretty easy to obtain. Atleast Gen V actually has you working for your powerhouses instead of "Let me trade a Magmar from my friend's game with a Magmizer so I can have Magmortar before the E4 LOL".
And for the people who aren't aware of B/W at all, I don't see the high evolution levels as such a frustration for them as more of a well-earned prize for training their Pokemon so diligently.
Basically, Gen V has raised the bar to more of a "Dragonite" standard, if you will. Back in Gen 1 and 2, if you wanted one of the game's most powerful Pokemon, Dragonite, you had to work extra hard, but the pay-off was great. However, considering the amount of work you'd have to put into it, a lot of gamers shrugged it off or just traded for Dragonite. NOW, a good 70% of the Gen V Pokemon are close to this standard, making the effort more of a basic thing than a "this is abnormally hard, wtf?!!!?!?!" thing.