'Most popular' view since last X days
You may want to take a look at the Radioactivity module and see if it works for you.  It defines a "hotness" for a node, and a "halflife" that the "hotness" wears off at.  This attempts to account for popularity over time, instead of raw page views.

For example, a popular blog post from a few days ago will be more "hot" than a wildly popular blog post from last year that had more page views.

Time-decay is configurable, and it integrates with Views.