I believe (?) the difference between a chimps DNA and a humans DNA is only about a 5% difference.
I am pretty sure it is 1.5% i heard a program a while back on NPR that was talking with (i think ) Bush's National Science advisor (an oxymoron i know) and he illustrated the point that if there is life anywhere else, it is unlikely we can relate to each other in any way whatsoever. If anybody has read Poul Anderson's "Boat of a million Years" towards the end there are two really important lessons to know.
1. Without faster than C travel, the reality is that anytime it takes 14 years to get somewhere, (and 300 years on earth since we are talking about relatavistic time) it kind of makes you think "is this REALLY important?"
2. Whatever aliens we may meet... are likely to be so different in every way that even the most basic communications will take years. (certainly much longer than it took Kevin Costner to learn the native american tongue.)
And yes, Avatar seems to be a real fantasy piece, but my point is that if you take just a little bit of time to incorporate some sort of reality into it (like probabilites of this physical universe.) then the story can be so much better.
Whether it was removing the "shared experience" kicker from Contact, or building the Enterprise on earth in that star trek movie, writers keep making these little stupid expediencies that really hurt the story.
I am not saying that i need to think that James bond really does all that stuff, but the one movie where he swam out of a submarine all the way to the surface... it made me swear off the movie franchise all together. (ok, i saw casino royal and the "non fantast" nature of the stunts etc. was a big appeal) same with other movies. it is either childrens fantasy or a movie with some grounding. that way i can get into it.