how much cgi is too much?

one of the things I appreciate about RS is his insistence on using physical sets/props and not relying too heavily on cgi. I know Prometheus will be unique in that cgi will be necessary for a lot of the fx and space shots, but I also know from reading the many articles out there that the set for Prometheus was pretty large which means there will be a lot of practical model fx. I think Ridley knows that physical fx are far more scary than cgi fx. This has inevitably made me curious how the space jockeys will be rendered and how many of the creature effects will use cgi? Does this make or break the film for you? I personally don't care for the heavy use of cgi. Alien 3 and 4 are good examples. We've all come to appreciate just how visceral and real the xenomorphs are, even if it's a guy in a rubber suit. However, in A3 and 4 there were elements of cgi aliens that were quite laughable. granted, these films didn't rely too heavily on cgi but the fact that they were there messed up the continuity for me.