Having (re)watched all three Wright/Pegg/Frost films within the same 24 hours, I will venture that:
Shaun of the Dead has the most classic lines and references.
2. Hot Fuzz was the funniest and most generally enjoyable to watch.
3. The World's End seemed the highest budget with the most action:...
Aside from fleeting cameos from conical iced cream lollies, The World's End imported little from it's predecessors, beyond the falling over a fence gag and the cast (notably Bill Nighy as the authority figure who Pegg's lead rebels against). Apparently there was a deliberate exclusion of external references and influences in production, so be warned, this is not a Spaced style geek-out.
I might have found more delight by entering the cinema totally plot naive; while the trailer did a very faithful job of portraying the nature of the film, it did so at the expense of telling most of the jokes and the entire story, baring the stilted conclusion, which I found dull - too earnest to swallow as satire.
There is a stereotypically false dichotomy between having a "good time" and growing into a contributing member of society. The former is exemplified by their rip-roaring adventure binge, piloted by Pegg's washed up Peter Pan, who brow beats Frost's co-lead back into the fold, despite understandably deep-seated misgivings. The latter is a trite portrayal of lonely busy-work in a soulless, corporate Greyland.
To be sure, most of the humour rests upon how anachronistic pitiful the immutable high-school legend becomes. But ultimately Mr King is vindicated, crowned triumphant, via a drunken remonstration, so obnoxious, the powers-that-be are forced to cut all connections to Earth, exploding all electronics, thus condemning humanity to post-apocalyptic purgatory.
When reviewing the film as an intellectual exercise, one can easily start to form arguments about, for example: how the superficial ravages of ageing don't illuminate people's interior yearnings that are every bit as vital as a teenager's, and maybe adults should all try to remember to enjoy life, via reminiscing, if necessary... The homogenising blandness of globalism, etc... In practice, I found the agenda of arrested development to be more appalling than the creeping suffocation of an alien panopticon. Maybe the theme of unrealised personal potential struck a little too close to home.
Perhaps I should just imagine that all the events beyond his group session induced epiphany, in the opening scene, are merely the decreasingly coherent hallucinations of the pitiful protagonist, wasted on industrial cleaning fluids and bleeding out from re-opened wrists...
"How The World's End rejects 'drunken, misogynistic' manchild films" (see last 3 paragraphs) - so the ending was definitely intended as a satire (of The Hangover, Old School, etc, neither of which I've seen). I think that got lost in the different bits and twists they tacked on... Couldn't be my fault for going into all films, these days, with no expectations of interpretive depth.