I disagree with the answers that say "There's no difference."
In both cases, you should critically evaluate the content with respect to correctness, reliability, etc. However, there is a difference with respect to the nature of the content.
Wikipedia (for most topics) serves as a tertiary source. That is, it aggregates primary and secondary sources on a topic, but doesn't add original content or interpretation. (In fact, it is against Wikipedia policy to include original content or interpretation.) In these cases, you should find and use the original source, to verify its contents and to give credit to the real authors.
Dedicated wikis on pop culture often do contain original content. And quite a few Wikipedia pages on pop culture do as well, even though they aren't supposed to (see e.g., Mythology of Lost).
For example, the Lost wiki contains a great deal of interpretation and commentary (e.g.: an analysis of recurring themes in the series) - not just a rehash of the episode plots. This makes it a secondary source, not a tertiary source.
You can use this original content (having critically assessed its correctness and reliability), and of course if you do, you should cite it.
For example, suppose you are writing a paper on "Use of the flash-forward technique in early 21st century television" and you read the following on the Lost wiki (or on an equivalent page on Wikipedia):
In Lost, the flash-forward technique was introduced in "Through the Looking Glass", although it wasn't made clear that it was a flash-forward until the end of the episode. The first episode to feature a flash-forward that was clearly shown to be one from the start was "The Beginning of the End". "Ji Yeon" was the first episode to intertwine flashbacks with flash-forwards, although the flashback element was only clearly revealed to be in the past at the end of the episode, making its temporality a plot twist.
Even if you then go on and watch the episodes "Through the Looking Glass," "The Beginning of the End," and "Ji Yeon" yourself, or read the episode scripts (i.e., verify the correctness of the claim by checking the primary source), you still cannot claim in your work that you identified the use of flash-forward in Lost all by yourself! The wiki page in this case is a secondary source with an original analysis and interpretation, and you should cite it as such.