If you read not only Enders Game, but the following books, specifically Speaker for the Dead (EDIT: It may be Xenocide that I am referring to here) you will see that it isn't just Alien Fear. While yes District 9 was fairly realistic for what we might expect in one situation, Enders Game is completely realistic in the situation posed in Ender's universe. Ill briefly explain what happens and why if you are interested in knowing.
Enders Game takes place 70 years after a second invasion from the Formics. The first invasion was to scout and begin terraform the planet, the second was a colony that had already been on its way before the first arrived. The humans had no idea of this and saw it as 2 attacks. Since there was no communication between the 2 races there could be no negotiating. So the humans decide to launch their own attack against the threat, and end up wiping them out.
Later in Speaker for the Dead Andrew finds the last remaining egg of a queen and learns of their story (they finally found a way to communicate with us). Since they were more of a hive colony, with a queen controlling every drone, they couldn't see that we were intelligent as well. They thought at best we were disposable drones. They didn't realize this until after the second invasion, in which point they stopped. But it was to late since the humans launched their attack already.
The later books go on to show how different views and propaganda can change human perception of things. But what I have explained is very fitting of humans, possibly even being to kind. The humans, with no communication to the Formics, fought with all they could against them. But our technology was primitive at the time, in fact a lot was learned from the Formics. And seeing this constant threat, we launched our counter attack to end it once we could. In 'Earth Unaware' (the story of the first invasion) you see how even from the first interactions, the humans perceived the Formics as hostile, and rightly so. But like I said, it was essentially due to miscommunication from two completely different species.
Now, our first alien interaction may go better. But it depends on a number of factors. We think and communicate in certain ways, and if the aliens fit our general conception of this, then sure, they may be peaceful or at least try to communicate at first. But we have nothing to support they will. We cant even communicate with other species on our own planet easily. (and yes there are a few that can learn to communicate with us) What we are talking about is a species that has evolved on a different planet entirely. Their evolutionary path will most likely be completely different, to the point we may not be able to comprehend them.
So not only would we have to think about communicating in the same manner, we would also have to precieve each other as an intelligent life form before we attempt to. I, along with many others, would like to think our first interaction will go peacefully, but we have no guarantee of that.