These are both obviously still super impressive (although man, Avatar is starting to look a little rough if you look at some of the environment work there. 7 years!) but it amazes me that we *still* can't quite make CGI models look like they're really interacting with ground. In motion and with good direction/quick cutting, we barely notice it in motion. But look at the T-Rex's foot, and the Na'vi's hand. They just don't look like they're truly touching the surface the character is meant to be resting on. The lighting just isn't complex enough. This is the next big hurdle that needs to be overcome with CGI for true photorealism. It's not a knock against these movies that it's noticeable (especially not for Jurassic Park, considering its age) but it's still crazy to me how much CGI characters stick out against backdrops still.
Take Gollum, for example. Considering The Two Towers is 14 years old now, Gollum is still incredibly impressive, particularly his expressiveness - but look at how awkward his hands and feet look in full-body shots (which are, wisely, avoided for the most part in the films):
Watch
this scene and notice how well they hide it. It's a good thing they did, because in the brief moments where you can pause and look at how he interacts with the environment, the shadows just aren't believable in the slightest.
For a more recent example, check out how much TARS sticks out in Interstellar, which I would venture is one of the best looking films of 2014: