The Borgias, Sky Atlantic, Saturday<br/>How Hip-Hop Changed the World, Channel 4, Friday

It is Rome, 1492. First scene, and the pope is, cough cough, on his death bed, cursing with his last breaths how corrupt cardinals will "fight like dogs for this throne". Second scene – bonking. Because that's how historical dramas work now, isn't it? Lusty romps, thrilling violence, scandal and intrigue, with a scant regard for historical accuracy but great, glossy production values.

The Borgias, from the makers of The Tudors, would seem to fill these criteria; its cast members are grandly thespian or youthfully good-looking. And, with a story about greedy, grandiose wannabe popes, there's plenty of opportunity for backstabbing betrayals and swish costumes.

Jeremy Irons stars as Rodrigo Borgia, a cardinal after the top job, and willing to pay for it – as we see at rather tedious length. But Irons does have some fun, his suave, buttery tones manipulating others or wryly acknowledging his own deliciously sinful approach.

Elsewhere, however, the acting and script feel about as substantial as a communion wafer. With power struggles, sex, assassinations and sibling rivalries, it should, at least, be racy and fun. Yet the storyline often feels curiously ungripping.

It's hardly overburdened with great female characters yet; as the mother of Borgia's children, Joanne Whalley has all the emotional expression of a hassock, making an exchange in which she realises she's lost her lover seem more as if she's mislaid the keys to the papal carriage. The daughter, Lucrezia (Holliday Grainger), is a skimpily drawn ditz. They all look lovely, of course, and the whole thing is handsomely done: gold everywhere, grape-festooned feasts, nubile extras cavorting in wine....

But for a drama revealing the rotted away, empty core of a religious society that has become simply concerned with outward wealth, The Borgias holds up a strange mirror; it too seems concerned only with ornate surface, masking a hollow heart where a story and inner character life might have flourished.

All is not quite what it seems with How Hip-Hop Changed the World, either. From the title I thought this two-hour special was going to be some serious, in-depth exploration. Actually, it follows Channel 4's tried and tested "50 greatest moments" format, starting with the insignificant (the graffiti origins of the 2012 Olympic logo) and gearing up to the most important (apparently Obama getting elected was down to his love of Jay-Z, or something). The likes of Snoop Dogg, Nas, Tim Westwood and Mark Ronson pop up as talking heads, while presenter Idris Elba ruins any coolness garnered from The Wire with his down-with-the-kids attitude.

Surely a chronological approach would have been more sensible. The top 50 thing, as voted for by God knows who – Jessie J and Dappy N-Dubz presumably – means we jump around the decades skittishly. There was enjoyable stuff here though; nostalgic moments all round, while for entirely unstreet girls from Welsh mountainsides like me, segments on technical developments – the origins of sampling, breakbeat, scratching – were embarrassingly informative. Others, however, felt unsettling: a lesson in how Run DMC made Adidas trainers a desirable uniform didn't seem such a happy marriage of music and commerce with a charred and looted Foot Locker on the corner.

I'm not suggesting Run DMC are an underlying cause of rioting, but the programme-makers do have a point, even if they make it in a sketchy, surface-skimming manner. Hip-hop clearly changed the world – and surely in more than 50 ways.