I am Legend is an interesting movie.
Its first half, where Will Smith seems like the only human left, is great. The zombie-like infected humans are a bit odd and not too interesting. But the ending of the movie sucks. What was that about God there? That part reminded me of the movie Signs. A much better ending would have been like that of the book where a perspective change makes him realize that he’s the monster in the new world.
I would rate the movie 6/10.
The feeling is mutual. I, like you, was disappointed with the ending as well. Especially after they built up the hype so much, I was hoping for something more interesting.