Troy may be inspired by Homer's Iliad but definitely not based on it.

Rating: Null/10 (17 May 2004)

Here are some of the Pros of the new film:
Patroclus is present and is at least dealt with as a beloved cousin.
The story focuses on Achilles, Hector, and Agamemnon with sufficient homage paid to the questions of duty, honor, and glory rather than the love between Paris and Helen.
The cinematography and special effects were good but, IMHO, not really superior to those used in the USA miniseries "Helen of Troy".
There was much more focus on Hector as a loving husband and father as well as skilled warrior and Andromache and Astyanax were nicely represented although I would have treasured a scene of Hector accidentally frightening Asytanax by appearing in his gore-covered armor as related by Homer.
Achilles was far superior to the bald, mindless brute portrayed in USA's "Helen of Troy". Even though I personally feared that Brad Pitt was not my mental visualization of Achilles, he actually portrayed a conflicted hero quite well. Eric Bana's screen presence as Hector was also equally riveting (as one of the other film critics pointed out). I liked the actor who portrayed Hector in the miniseries but his part was deliberately overshadowed by the focus on Paris.
Here are some of the cons as I perceive them:
The screenplay had eliminated almost all reference to the role of the divine in the events portrayed. There was no judgment of Paris. The gods did not rescue Paris by obscuring him with fog during his duel with Menelaus. Most of all, sadly, there was no flame-wreathed Achilles standing and shouting out his grief for Patroclus. The only "paranormal" reference that I remember was Hector's admission that he had seen his fate in a dream.
Although the Iliad does not mention Agamemnon's sacrifice of Iphigenia, that is one of the events told in the collective Trojan War myths that was included in USA's "Helen of Troy" that I found quite poignant and that provided much more depth to the character of Agammenon portrayed by Rufus Sewell. I thought Brian Cox's Agamemnon was rather one dimensional  simply the personification of an individual totally corrupted by power.
I also preferred James Callis' personification of Menelaus to hold more humanity than the brutish warrior portrayed by Brendan Gleeson.
Cassandra and her torment about forseeing the destruction of Troy was totally omitted. I thought this aspect of the story was incorporated quite effectively in the TV miniseries.
Since Iphigenia was omitted, a vengeful Clytemnestra was also omitted. Again, the TV miniseries provided a more dramatic resolution than this movie.
Aeneas was portrayed as a youth. In Homer, Aeneas was second only to Hector in Trojan military prowess. The boy in this movie doesn't even look old enough to have taken part in the fighting and how he was managing to pack his aged father on his back is a mystery to me. He was also too young to be leading a son, old enough to be walking unassisted (Ascanius).
Small spoiler ahead.
The movie makers decided to kill Ajax, in this film just window dressing - a huge man slinging a huge hammer around, in one of the battle scenes instead of portraying his suicide after the sack of Troy, committed because he was not awarded Achilles armor. There has been a lot of discussion about Sean Bean as Odysseus starring in a sequel. This negates the possibility of incorporating any emotional meeting between an unforgiving Ajax and Odysseus in the underworld.
I still enjoyed myself and simply hope that some day someone in Hollywood will have the common sense to film the classic in its original form.