By Neil Smith Entertainment reporter, BBC News

With budgets routinely topping $250m (�125m), the studios' reluctance to gamble with unfamiliar material is understandable.

In a climate of spiralling production costs, vast marketing outlays and increasingly narrow windows of box office opportunity, the stakes have never been higher.

But how many of this year's blockbusters will realise their potential? The BBC News website offers its guide to the runners and riders.

Release dates: 4 May (UK & US).

Key players: Tobey Maguire, Kirsten Dunst, Sam Raimi (director).

In a nutshell: The web-slinging superhero is back to battle an old foe, an evil doppelganger and a nemesis made of sand.

The buzz: Though critics have voiced reservations about its surfeit of villains, the third instalment in Sony's comic-book franchise is guaranteed to start the summer with a bang. Its early release date gives it a head start on its nearest competitors.

Release dates: 18 May (US), 29 June (UK).

Key players: Mike Myers, Eddie Murphy, Chris Miller (director).

In a nutshell: To avoid being crowned king of Far, Far Away, grumpy ogre Shrek sets out to find a more suitable heir to the throne.

The buzz: Shrek 2's $920m (�460m) takings made it the most successful animated film ever, raising the bar for a third helping that boldly opens in the US slap-bang between two other eagerly-awaited 'three-quels'.

Release dates: 24 May (UK), 25 May (US).

Key players: Johnny Depp, Orlando Bloom, Gore Verbinski (director).

In a nutshell: Captain Jack returns to lead a rogue's gallery of pirates drawn from the four corners of the globe.

The buzz: Rumours of a three-hour running time and a $300m (�150m) price-tag have made Disney's trilogy-completing swashbuckler the talk of Hollywood. But with Pirates 2 breaking the $1bn (�500m) barrier last year, producer Jerry Bruckheimer won't be paying much attention.

Release dates: 8 June (UK & US).

Key players: George Clooney, Brad Pitt, Steven Soderbergh (director).

In a nutshell: Smooth criminal Danny Ocean rounds up the usual suspects to make casino owner Al Pacino pay for double-crossing a friend.

The buzz: Screening out of competition at Cannes will be the perfect launch pad for an all-star heist comedy that Clooney and Soderbergh promise will be an improvement on the critically slated Ocean's 12.

Release dates: 27 June (US), 4 July (UK).

Key players: Bruce Willis, Justin Long, Len Wiseman (director).

In a nutshell: Veteran detective John McClane teams up with a young computer hacker to foil a hi-tech terrorist plot.

The buzz: With more than a decade separating the third Die Hard from this latest instalment, nostalgia will be a key factor for a Fox release that opens in the US on the same day as Pixar's Ratatouille, and a week before Transformers.

Release dates: 13 July (US & UK).

Key players: Daniel Radcliffe, Emma Watson, David Yates (director).

In a nutshell: The boy magician faces official opposition as he attempts to marshal forces against the evil Lord Voldemort.

The buzz: Opening just ahead of the final Potter book's 21 July publication date certainly won't hurt the fifth instalment in a family-friendly franchise that has so far earned $3.5bn (�1.7bn) worldwide.

Release dates: 3 August (US), 17 August (UK).

Key players: Matt Damon, Joan Allen, Paul Greengrass (director).

In a nutshell: Jason Bourne's quest to uncover his past is hampered by a new generation of agents with orders to kill him.