I liked the original Avatar movie, but the plot for this sequel was totally unimaginative and predictable. Here's the entire story in one sentence: Colonel Quaritch leads a mission to take revenge on Jake Sully which, three looonnnnnng hours later, culminates in a giant battle. The end.
The effects were decent but the script was simplistic and often plain old dumb. I gave up after about an hour and, with my phone respectfully dimmed and covered so as not to distract those around me, decided instead to read the news, play a word game, and take a nap. After all, I had plenty of time on my hands to do so.