Not all franchises are created equal. The release of 'Nativity 3: Dude, Where's My Donkey?!' shows that sometimes audiences just want a bit of silly escapism rather than more ambitious attempts to wow us with effects and bigger/better plotlines.

Nativity 3 Cast
Martin Clunes stars alongside Catherine Tate and Marc Wootton

This certainly isn't unprecedented: other thoroughly silly franchises include 'Alvin and the Chipmunks' (3 movies), 'Spy Kids' (4), 'Step Up' (5), 'Scary Movie' (5) and 'Tyler Perry's Medea' (7 and counting). And an argument could be made for including 'The Expendables' (3 and counting) on this list.

More: Watch the trailer for 'Nativity 3: Dude Where's My Donkey?'

The usual franchise formula is for a great film to be followed by ever-diminishing returns, like 'Jaws', 'Rocky', 'The Terminator', 'Alien', 'Rambo' and 'Hannibal Lecter'. It's much rarer for a franchise to launch after a mediocre start (see 'The Fast and the Furious', with a 7th coming soon and more planned).

Then there are the ones that keep going even though were pretty bad to begin with, like 'Saw', 'Paranormal Activity', 'Underworld' and 'Resident Evil'. And there are other franchises based on book series that come to a natural conclusion, like 'Harry Potter', 'Twilight', 'The Lord of the Rings' and eventually 'The Hunger Games', 'Divergent' and 'The Chronicles of Narnia'.

More: See pictures from the 'Nativity 3' Premiere

On the other hand, some franchises are unmissable and seemingly open-ended. We're still looking forward to the next chapter of 'Star Wars', 'James Bond', 'X-Men', 'Star Trek', 'Marvel's Avengers', 'Bourne' and 'Mission: Impossible'. Whether we'll be quite so excited about 'Nativity 4' is still to be seen.