While I only half-agree with the thesis of OP and everyone else, I'd like to muddy the waters further by bringing up a problem I had that started with the pokemon in the 4th generation. It seems like a number of evolutions weren't redesigned to be "bigger and better," just "bigger," or more accurately, fatter. I put forth just a few examples that stand out to me.
Lickilicky, the evolution of 1st gen Lickitung. You'll notice that it's incredibly fat with a head a fraction the size of its torso. Attached to this huge body are arms that couldn't come close to touching, given their size relative to the torso, and underneath are a couple stumpy legs that, ridiculous musculature and bone strength notwithstanding, couldn't hope to hold up the rest of the body and tongue. Also, if you compare the D&P sprites of Lickitung and Lickilicky, it seems to suggest that the evolution's tongue is smaller.
Honchkrow, the evolution of 2nd gen Murkrow. Once again, tiny head, body the size of Minnesota. And, once again, the limbs present a problem; the sprites suggest that the wings are severely undersized for a bird that large. I'm no physics expert, but unless Honchkrow uses dark-type powers to help it fly, those wings wouldn't even get it off the ground, much less in stable flight. Furthermore, I'd like to point out that it seems like at least 75% of its body are in FRONT of its feet. Flying is right out, but it looks like simply standing upright would be nigh-impossible.
Purugly, the evolution of 4th gen Glameow. Both look silly, but Purugly, I think, is just outright stupid. One of the traits most commonly associated with felines, possibly THE trait, is how agile it is. Purugly, in game, is a relatively quick pokemon, in spite of the fact that it looks like a big lump. The legs are short and fat, good for power, not speed. The head looks a little off, but at least it's not way out of whack with the rest of the body. I suppose I don't have too much to say about it, I just can't get over the fact that the only appreciable difference, visually, between Purugly and the first stage form, Glameow, is that it is REALLY GODDAM FAT.
As for the 5th gen starters, I'll admit they all look weird, to the point of looking clownishly silly. However, the same could be said for almost all the starters, yet more or less all of them end up looking fairly intimidating. As such, I think it's best to withhold judgement until B&W comes out. HOWEVER, that doesn't mean I can't pass judgement on the 5th gen legendaries.
Reshiram, the white legendary, is a giant chicken with wings that end in fingers - take a close look at the claws - with a distinctly jackal-like head, and a tail that just boggles the mind. Oh, and the weird crotch-feathers.... do I need to say anymore? At the very least, the head is more or less in proportion, as are the wings/arms.
On the other hand, we have Zekrom, the black legendary. I think its tail is also thoroughly ridiculous, but the rest of it looks impressive, if a little over the top.
You know, I think I know what my problem with the newer legendaries is: They all look intimidating, but that's just because of how they look. If we remember back to the very first generation, we had the three legendary birds, each of which looked relatively simple, but you could tell they were not to be trifled with. Then of course, there was Mewtwo. A design as simple as they come, yet the biggest badass in RBY. He didn't need billowing mists, silly tails, none of that. And yet, catching Mewtwo was, and still is, one of the biggest challenges in the entire Pokemon series.