I would like to know if i should build a content rich site or a review site to promote affiliate products? which would likely to get more sales?
If you can find the right product to review and are decent at writing sales pitches, I'd go with the review site. On the other hand if you can't find anything but have a topic you are passionate about that isn't already saturated go for the content-rich site.
I think first is much preferable. Rich content will bring much traffic, so affiliate sales will grow up. Relevant affiliate links will work better.