Here’s the list of top 100 iPhone apps. There are some pretty interesting entries.. the pull my finger and similar apps (e.g., Amateur Surgeon) are perhaps where they are due to recent slashdot’ing about Apple deciding suddenly to approve “limited utility” and adult rated apps.
Roughly 1/3 of these are useful utilities. 1/2 are games. 1/3 are completely frivolous. Yikes.
The app rankings are based on number of downloads. Apps on this list can see hundreds to thousands of downloads per day, and are mostly priced on the cheap.
There is some info online about how well these apps do (or don’t do). Here’s one example for a simple basketball game priced at $0.99, that generates 60-350 sales per day (at least when the piece was written).