That option appears to be gone now; possibly because of all of the other changes with the newsfeed and everything else. The developers at Facebook have turned their attention elsewhere for now.
Oh, the times they are a changin’!
What to do? You could go to every single page, one by one, and unlike them that way. Oh, what a pain!
The good news (hey, you knew I had to put a positive spin on this, right?) is that there is a slightly easier way.
Here we go:
Click on activity log on the wall of your personal profile (it's near the bottom of your cover art) Using mine as an example here.
Click "like" on the left side of the page.
Then click pages and interests. Directly to the right you'll get a list, starting with the most recent page you liked and going back in time.
And you thought I was going to show you all my likes, right? Nope!
If you hover over the name on the left side a pop-up appears with the icon and cover art of the page.
Note: In this example I'm hovering over the name of my sister page, Groovy Reflections. Rest assured that I won't be unliking that page! DO think about the implications of unliking a page: Does it belong to a friend of yours? Was it a "like for like" therefore you risk losing a "fan"?
And yes, this is a time consuming endeavor. If you have hundreds of pages to rummage through, go through a small chunk to unlike or keep per day (maybe choose to show in news feed?). Spend about five to ten minutes so it's not too painful.
Maybe Facebook will introduce a new way to maintain your liked pages eventually. One can only hope. On a brighter note, The Romantics "liked" you in their big hit tune (see below). Feel free to "like" us and drop by our by our website, or say hello on Twitter, Facebook, or Google+.