The Borgias is visually stunning, and history couldn't have given them a better script. With the show's budget, cast, sets and costumes, it could have been a masterpiece, but they are butchering the history and also turning it into a soft-core soap opera. Admittedly, everyone wants something different from the show--more racy, more diabolical, more historical--but in my opinion staying closer to what is known is more interesting than anything that could come from the imagination of screenwriters. Yet it is likely the more trashy aspects which help generate the higher ratings...
According to Tom Fontana (the creator of the Canal+ version) when he originally met with Neil Jordan (the director of the Showtime version) to discuss working together, Jordan said "he didn't care about the history; he said he'd make things up." That explains a lot about Season 2, as it is even more a work of fiction than Season 1 (the attempted murder of Rovere; the artisan lover; the burning bull; the falling chandelier; the plaster canons; Cesare's nun; Lucrezia on St. Peter's Chair (loosely based on her father briefly putting her in charge of the Vatican while he was away); the destruction of the gun powder; the Pope in Florence; Cesare's envoy to Forli; Micheletto in the graveyard! Cesare hanging out in Florence with Machiavelli; Juan besieging Forli and torturing Caterina's son (this episode is very loosely based on an uprising which occurred in Forli in 1488); Rovere's food-taster; Juan's drug problem, etc). It might be more enjoyable to watch it as a purely fictional work, but even then it is silly that the Pope and his Cardinal son have to bang every woman they come across.
François Arnaud's Cesare is excellent, understated, composed, convincing and dignified. Yet, the real Cesare must have been somewhat more intimidating since he had had a reputation for cruelty (though I realize he is still only a twenty-year-old Cardinal at this point in the story).
The acting of Micheletto is so good! His character seems right on (except their little addition!?).
The actress who plays Lucrezia is very good--very noble and lady-like--but she's given nothing better to do than chase after guys.
Juan is portrayed in an almost comic fashion as a sort of brutish slimeball (how is it that no one involved in the production pointed out the absurdity of this performance?).
Jeremy Irons is wonderful and makes a plausible Alexander, though they don't draw out his ambitious side much.
The portrayal of Savonarola was great, and this is the one case where it could be said that they improved upon history, since it was interesting to see him go through with his trial by fire, something he agreed to but that then never happened. Instead he was burnt, much like we saw, though in Florence rather than Rome.
Florence became a Republic in 1494 when Charles VIII invaded Italy and the Florentines chased Piero de' Medici out. Machiavelli didn't get his office as Secretary of the Florentine Republic until 4 years later, after Savonarola was executed.
Since it is not known who killed Lucrezia's lover--he was found drowned--it is interesting that they made it Juan since the rumours usually circle around Cesare.
The French King, Charles VIII, is great (and hilarious) but he was actually only twenty-four at the time. This is another case where history was more interesting and compelling. Why change it? At twenty-four, Charles was young enough and impetuous enough to be encouraged to take Naples against the advice of his better counselors. For those reasons, Canal+'s Charles is more accurate and interesting.
Another change for the worse: Juan's death. The actual circumstances around his death are much more interesting. For one, where is his mysterious masked man and the man on the white horse? What was most enigmatic about Juan's death is that there were only ever speculations about who did it. On this point the Canal+ version is very faithful to the known details, though they then add a weird interpretation.
Without Juan, season three can only be better, but poor Cesare, his name further blackened when there is no real evidence he was the guilty one.
And it's not really a cliff hanger if you know the pope doesn't die until several years after Savonarola's death...