There seem to be several other "100 Riffs" clips on YouTube that I haven't investigated. What I find interesting about this is that it offers a cross-section of typical 'riffs' in pop music. Most of these take their structure from blues--you will probably notice that the same gestures keep coming back again and again. These are mostly short phrases and, in the absence of the bass and drums, tend to show their weakness as melodic ideas, being often fragmentary and with incoherent melodic shape. There are a few licks that have a strong harmonic component--one in particular uses secondary dominants, but I forget which. Occasionally a lick will recall traditional harmony, especially some of the very earliest ones. A bit of jazz harmony comes in now and then. Notice how often a simple melodic idea is sometimes harmonized with bare 4ths or 5ths.
If you were teaching a course in popular music, this video would be an excellent resource.
UPDATE: After listening all the way through the clip above I found myself humming one of the licks for the rest of the day. Which one? Not "Day Tripper", oddly enough, which is an occasional 'earworm' of mine. (An 'earworm' is a melody that keeps circling round your brain. Usually the only way I know to dislodge one is to hum the subject of a Bach fugue. That usually gets rid of it.) No, the lick that kept bubbling in my brain for the rest of the day was "Layla". I started wondering why and I think, when I get a chance, I'll put up a post analyzing the "Layla" riff. But I don't think any of us will be too surprised if the best guitar lick of the last sixty years turns out to be by Eric Clapton!