In the abstract, "from" and "in" are nearly interchangeable in those two sentences from a strictly grammatical perspective (either could grammatically be used, although there would be different nuances in meaning). However, the usage you show "sounds" right" to a native speaker in terms of which of the two words to use for each case. That is because of what we would assume are the missing words behind the meaning:
Tonight we've got Mariela with us to talk about her favourite films [selected] from [those she saw in] the last ten years.
The "from" would refer to the collection from which they were selected more than the time period explicitly mentioned. The time period defines the collection.
It was the most unusual film [produced] in the last ten years.
Here, "in" refers directly to the time period and means "during".
Note: there are various interpretations and word choices people might assume for the missing words. The point here isn't the literal choice of the missing words, but the general sense of why "from" and "in" seem logical. "From" would seem to refer to selecting from some collection defined by the last ten years, while "in" would seem to relate to the film becoming available during the last ten years (direct reference to the time period).