Dawn of the Planet of the Apes so much that right after I watched the earlier movie in the series, Rise of the Planet of the Apes. While watching Dawn I was not aware of not understanding anything; there was no point of confusion. But seeing the first one I realize I would have enjoyed Dawn more if I had watched these in the proper order.
Rise shows us Caesar as a baby and his development in a human family -- which explains his tolerance and affection for humans in Dawn (which I didn't question but which now makes much more sense). It also explains his knowledge of events that led up to everything, and his ultimate position as alpha among the apes. In Rise we see several characters such as Maurice (my favorite) and Koba (such a perfect villain), which provides background for their relationships depicted in Dawn.
I was very charmed by and invested in Caesar's story throughout, and was not expecting that emotional connection. I guess he was just such a cute baby and little imp. Plus, a real range of feeling were conveyed by his eyes.