Two pages as a good rule of thumb. Large CV's with lots of text are off-putting, not a good idea when you have stiff competition. Consise, clear, well-organised and focussed CV's give a very good impression that make it stand out, as well as helping at interview. In my experience and particularly when there are large numbers of CV's, employers have two piles, those shortlisted for interview/further review, and those being past-over. Clearly you need to be in the 1st pile
CV's are a sales job in themselves, you need to convince employers you are a good buy, how you present yourself in a CV makes a significant impression, consciously or unconsciously wih them. Buying is as much an emotional decision as a rational one. You need to assure an employer you are worth buying, and make them look forward to seeing you at interview. They want/need to make a good decision, and fear making a bad one, you need to address this and provide them with the reasons they need to feel they are making a good choice. As much as possible gear the CV to the particular job, use the cover letter to do this. Standard cover letters are generally a bad sign and often off-putting. It doesn't show any clear interest in this particular job on your part, and imo it's a sloppy lazy job. Not a good start with an employer who is looking for a new, effective, committed employee.
Keep cover letters brief and punchy, make the interviewer want to read more, remember they are against the clock, and you are competing to get into the 1st pile. CV's and the cover letter should make the interviewers stop and look, it should begin to convince a potential employer you are a good buy. Take time to do it right and tailor it.