I'm creating a review site and there are around a dozen products for my niche. Would it be too much to include a dozen products and a review for each one on my review page? Keep in mind I'm only targeting about 4 products.
it would be too much if you were to say all of them were great, create reviews of them all but only recommend two or three of them
If you review more than 3, you will rather confuse you visitor. My trick is to review 3 products and keep lowest priced product at 2nd, so if a visitor is price conscious he will buy 2nd one rather than move to another website.
It depends on the type of review site - check out Chris Rempel's Conduit Method and you'll see that it's possible to review lots of products and still be successful. Here's the link (not aff) http://www.thelazymarketer.com/vip-conduit/
Always limit to no more than 5 products. In most cases, I will cover only 3 products and they tend to convert better. Too many can become too confusing.
It is also a good practice to include comparison tables that compare the pros and cons of the products you're pushing on your review site.
It doesn't matter if you have more than 5 products on your website. If you do good SEO, a lot of visitors will come from Google. I've setup a website moneymakinglibrary.net with more than 10 products in different categories.
If they are all on one page then 3-4 max. If you categorize everything nicely with elegant unobtrusive navigation and do SEO then you can put as many reviews as you want on a site.
My review site has 2 products. However most of the review sites I see online have at least 3. There are some other sites that promote 10+ products, but usually these are huge content sites and offer a lot of information plus reviews of products as well.