IMHO your resume must first match the requirements so that HR or recruiting agency can select it. You simply cannot have one resume, you have to change it for each requirement my rearranging, improvising and highlighting the stuff that employer is looking for. Always remember the hiring manager is not the first person to look at it, the first person to look at it is some low life, lazy HR person. They are probably looking for keywords in your resume to match the requirement. I have interviewed close to 50 candidates this year, we have hired about 15 contract resources this year. We can only interview what HR sends us. I knew some ppl how would be good fit for the job, they submitted their resume through some contracting companies but HR initially did not approve them, I had to ask that lady to pass on that resume so that my peers can review.
Now having said that, no one in my organization cared about the number of pages, we have accepted candidates who had 3 pages and some had 10 pages, it did not matter. We always looked at the last 2 max 3 project and what the candidate did there for candidates who had long resume. First page is pretty important, should highlight/summarize all out achievements and expertise (match the job requirement).
Once the resume was selected for interview no one really put too much emphasis on whats in there, everyone had their set of questions that they asked. Everyone judges the candidate from different angles and try to find out if you are a good fit. ppl will give you an opportunity and try to dig inside you to find out things that are not on the resume.