The film I, Robot originally had no connections with Isaac Asimov's Robot series. It started with an original screenplay written in 1995 by Jeff Vintar, entitled Hardwired. [1]
I likely would have enjoyed it more had I not been expecting an Asimov story on film. I like Will Smith a lot, but somehow he's been in multiple films that ruined favorite books from my youth (I Am Legend is another book that I love and that had an abysmal film adaptation...I don't blame Smith, though, as he did a great job even in a very cheesy film). I, Robot was also pretty cheesy even without the weight of trying to live up to Asimov's legacy.
But, then we got a closer look at them a bit later and they were flying through the air, bouncing off the walls, and just all around looking like cartoon monsters. I'm just not frightened by cartoons. And, it really killed the slow, calm, horror of the book for me. The things that made the book unique and scary in a way that sticks with you are just fundamentally different from the jump scares of the film.
The Vincent Price adaptation (The Last Man On Earth) remains the most faithful film version of I Am Legend, in spirit if not in specific detail. I don't really mind when a movie script changes some plot points or some character details to make it work on screen, I just dislike it when the spirit of the thing is thrown away and replaced with blockbuster tropes (which is my primary complaint about I, Robot, as well).
But, again, I thought Will Smith was excellent in the role. I just really hate what they did with the vamps.