Technically, that makes the basic figure the weak one... But it ties to the whole point that Rex is hyping a toy, which is hyping a cartoon/movie, which is hyping up kids...
The Crystal Skeleton was more like a fan wank then. It was available to mail in around the time of the film's release... And was revealed only after the movie. For hype factor, Rex is still the better choice I think as toys go...
Like I say, the Skeleton rocks as a set piece... it's kind of like being told you could mail away for a stand of chalices from the Last Crusade, or the ark maybe from Raiders. It's cool, but it's like a glorified accessory to another figure or something.
Rex is all about action, action figures, and building hype for a new toy line and a new movie/cartoon... As toys go, Rex is pretty outstanding. The collector in me digs the skeleton, but the toy fan in me appreciates Rex for what he is... And I'm not even collecting animated stuff.
Rex just reminds me of the cool stuff you could mail in for as a kid... The skeleton, not so much. It's more like the, "hey, I wanted that now that I'm 30 and it feels like my collection feels incomplete without it", crowd... if that makes sense.