"To what extent would you say online film reviews are postmodern?"

Online reviews are generally intertextual. They often refer to other films, either to refer to related films (e.g- franchises) or to refer to other films by the same actor or director. This may be due to films now a days being largely based on existing products, since high profile producers do not take risks and instead opt to put out work that is reliably"mainstream".

This fits into baudrillard theory of simularca, because  the reviews refer to other texts, and therefore are not completely original in their conception, as they are copy's of what the reviewer has seen. The films themselves are not totally original either, as they take inspiration from other texts (eg- Batman Begins was almost completely based on the comics).

In terms of hyperreality, Baudrillird would suggest that if we read a review of a film, then our perception of that film is based and influenced by that review. This i believe is incorrect, since people are aware that a review is simply someones opinion, and even if they are industry professionals, ones personal taste can always be a huge influence. The reliability of the reviews depends on the outlet of the media text, since generally more professional outlet can be relied upon to be more informative and reliable.