Well - ending one is the 'save mankind' ending and ending two is the 'allow evolution of the zombies' ending.
I like idea of the second ending but I wish he didn't escape - the death of the main character in this story (and Omega Man) is very important.
I like the first ending because he dies - it follows Omega Man more closely than it does the book because he dies to give the uninfected a chance at developing a vaccine / cure. It's a Christ parallel of course.
BUT if you read the book it is SO much better than either. The infected start to form a society, start to live with the disease and adapt. At the end he is captured and is to be executed - He sees that the infected are terrified of him - he is their Devil, as it were. An evil, murderous force that will, in time, become both the Creator and Devil in their myths (and thus the title I Am Legend makes sense). He ressigns himself to his fate and allows himself to be executed.
Much better.
I have not seen the second version of the ending, but I have to think I'd agree with this assessment. Everybody who's seen this should get Matheson's book. Of the two endings, I'd go for the first.
As for the movie, I saw it three times in theaters, and the first three-fourths of the movie is incredible, most the reason for that being the effects involved in creating the dead and empty Manhattan, and Will Smith's very human performance. But the ending, especially with the hokey part about the butterfly and the fight with the monsters wasn't as good.
On the topic of the appearance of the monsters: I think they look like steroid-jacked versions of Smeagol from
The Lords Of The Rings personally. I would have preferred human actors to play the monsters, even if they couldn't physically do what the CGI monsters do in the movie, if only because the monster effects in this look so second-rate to the other visual effects in the movie.