Hmm...
I know what you mean about the hips, I can imagine them ending up looking really... wrong?
I guess the thing about Riolu is that with the proportions it has (the huge head and teensy torso) the huge puffpants are a bit less noticable.
One thing I can say is that the legs on your drawings are particularly thick -- not that this is a bad thing necessarily, just that that sort of... realism will make it look less like a Riolu, and make the implementation of puff-pants difficult, as that is so much extra thickness! Waugh!
Making them thinner would probably just look unnatural, so well...
This random image I found kinda makes me think, if you just treated those puff things as the thigh area and made them only slightly thicker than the rest of the legs (which is what the thigh area is supposed to be -anyway-) then it'd be a pretty good balance between Riolu and human. It's hard to distinguish those as the thigh on all the official art I've seen so yeah... also this makes me think of Lucario with the more "realistic" anatomy!
Also, just noticed it now, on your street-fighter picture the nose seems too... high, long, pointy? I guess? Or maybe it just needs a sharper angle connecting it to the face. Anyway, I'm not quite sure, so I'll leave you to it. (:
EDIT: Also, with legs, uh... at least aim to place the hip area just above halfway! Like, if you've seen those triangle diagrams (as in where the hips are a triangle with one point at the bottom... well, actually maybe just think of some underpants or something) the bottom point should be
about on the halfway-line for the figure.
'NOTHER EDIT: I don't know good reference sites off the top of my head, but at a glance
www.human-anatomy-for-artist.com/ seems to be OK. But be wary that a lot of the pictures there are completely naked, so you should probably carefully view them in your own time and clear your history or someone will get the wrong idea. (: A quick look there showed me they had a decent sized section on fighting and martial art poses! Failing that, maybe just search the name of the position or move?