Truckin,
Those are tough questions. What works for one person, may not work for you. I think the best thing to do is try X number of reviews on your site to start out with. Do that for a month or two and then increase or decrease the amount of reviews on your homepage and see if there is a substantial difference in your conversions.
Just remember, people like easy to navigate sites, so 50 reviews on the homepage may not be the best alternative. What has been popular in the past and works well is a top 10 or top 5 or even top 3 reviews list and then text links to more reviews within the site.
In terms of creative, I think again that will be a case of trial and error. I tend to think players like the screen shots and logos a bit better, but a well designed banner can also convert very well. Just give everything a shot.
Kind Regards,