Popularity of a film is hardly a good judge of what the ride can be. Sleeping Beauty was not popular when it came out, and they made a castle out of it (which opened before the movie came out, but that's neither here nor there) and the kewlest scene in Fantasmic! spawns from it. Song of the South is only even HEARD of by a select few individuals, as it is not available the US, so very few people have even seen the movie, especially kids (I have never had the opportunity to see it), so I don't really see Song of the South as a blockbuster hit, but it made an incredible attraction. Given the money, Imagineers can do a lot with this. The problem at DCA was that they were building multiple E-Rides at DCA at the same time, and were building the mountain to boot, so didn't invest more money in better theming. Kali River Rapids has the best theming in the queue that I have ever seen, and the theming along the very short river is also very well done. It seems to me that they just started with a pretty bad theme, which was the problem. It's okay to have a background lesson regarding logging, but to base an entire ride's story on that was never going to yield anything jaw-dropping. They ended up with one of the funnest (not sure that is a word) raft rides ever made (I think it is wildly fun, though very short). Its changes were made very late in the game, as through much of the construction, it was still termed Tiger Rapids Run. When it became apparent that the tigers would not be effective for a raft ride (you would barely see them even when they were awake), it was far too late to have animatronic tigers that were even remotely believable. So, WDI had to scrap together a story very quickly, giving us the very fragmented ride today, where the queue is elaborately themed, then there is one show scene hastily put together (though it is well done), and chain saw sound effects in the queue that are supposed to pull the ride together. The idea behind this ride was awesome and it would have been breathtaking had it worked, but last minute changes created Kali River Rapids in the rush to get this ride open after initial views of Animal Kingdom were just "okay" (with its two rides). If they were to start out this new ride with a much better ride concept, which I think they have, and enough funding to carry it out (if Canada is willing to help with funding, that would be no problem), they could get an awesome attraction. Several areas of Grizzly River Run feature relatively slow-moving water, very conducive to show scenes. The ride, itself, is extremely fun and quite long. It would be a hit with more story, and Epcot is long overdue for a water ride where you actually get wet. Grizzly River Run is drier than Kali River Rapids, by the way. I got roughly as wet as I get on Splash Mountain.
I think it's a really nice looking ride
Grizzly River Run overall
Lift Hill
Grizzly at Night