What I really like about internet is the fact that you can get access to real-life data sometimes. For example what is best method for identifying most popular songs of last year?
For some it can be charts - but charts are always depending on radio listeners or radio genre. Another approach can be number of sold records, however that doesn't say anything about number of listeners, for example if song is really great, however album is really bad, people won't buy album and will download MP3 instead. Not talking about fact that most people don't buy CDs anymore (IMHO) and are buying\downloading MP3s only (and I think that number of downloads is much higher than number of purchases).
So for me best method to identify hits of last year is to review numbers from Last.FM (that have millions of listeners and is not focused on single genre).
Want to know more? Have a look at Last.FM Best of 2008.
Don't interested in movies? What would be best method to see changes worldwide or in your country?
Great idea would be to base it upon search queries - especially in case of big player such as Google (that is used by different people all around the world). I blogged about Google Trends already and when I tried to play with some trends of year 2008, I discovered very interesting press page called Google Zeitgeist that already did this job. Very interesting with details about each country :)