I reckon it’s seeing three good friends having a right old laugh and a Jolly time together, with a generous helping of friendly abuse.
Second is the hilarity of the things they get up to and what happens when somebody says “How hard can it be”
The cars? The cars come somewhere distant eighth or ninth.
I think you’re onto something. I have no interested in cars, but still enjoy an episode of Top Gear.
There’s something almost family-sitcomish about the combination of their three personalities (or on-screen personas). I’m not quite sure where to place a matriarch/patriarch divide, though 
The verbal humour is somewhat laboured. I think it’s the spectacle.
I know a TV producer who interviewed for Top Gear, and, when confronted by a typical scenario and how she would approach it, failed on three counts: a) too many in-depth interviews, b) £100,000 under budget, and c) no explosions.
Car and Driver magazine used to be extremely popular in the US when they had a somewhat irreverent bent; for example, unusual road tests (railroad locomotives, aircraft carriers, etc), pointless vehicle mods (dual-engine Honda Civic, V-8 Chevette, etc.), and adventurous road trips. In recent years, the irreverence was replaced by right wing/libertarian-leaning political rants of the “damn liberals want us all to drive hybrid and electric-powered econoboxes at 55 MPH” variety. An attempt at a Car and Driver television show was a dismal failure. Where Car and Driver used to disappear from shelves a few days after an edition was released, now it’s easy to find a copy. The publication doesn’t seem half as popular as it was in the 1990s and early 2000s.
Top Gear really reminds me of the old Car and Driver; good chemistry among the crew, irreverent and fun stories, bus still focused on competent reviews and a serious respect for the automobile.
I largely agree, but I don’t think you can discount the gear-head aspect completely. I mean, some of my favorite segments are when the Stig takes the car-du-jour through it’s paces and when the celebs do their laps. Also I like seeing them outline the pros and cons of exotics with a slightly more critical eye than your average car-honk magazine. It’s the personalities that make the show interesting and consistently watchable where other more staid auto shows get tiresome and repetitive, but without the cool cars and goofy mechanical stunts there wouldn’t be much for them to be snarky about.
The very high production values are part of it too. The filmed segments are beautifully put together.
They’re not afraid to give a car an outright bad review.
They turned a car into a space shuttle. 'Nuff said.
Top Gear sometimes gets within touching distance of this during the “news” section.
I watched that whole segment going “No way…nope, no way…fucking hell wooo!”.
Yeah, but they’re still funny when they do it. 
I have no real interest in cars. I don’t have a driver’s license and I don’t intend to get one unless either I or my job moves to somewhere where it’s more hassle to use public transport than go by car. I would also have to find some place to park the damn thing.
But I like to see beautiful cars, races, wacky experiments and people taking the piss out of each other. I watch it almost every week. Great fun.
Humour and audacity.
Their show could be a show about can-openers, and I would still love it.
Their secret is to take three brits, three $2000 ‘cars’ and drive through the Deep American South with sayings on the side like ‘NASCAR is rubbish’ and ‘I like boys’…then deliver dinner to the campsite by way of a roadkilled cow, strapped to the top of a Camaro…its juices leaking in through the T-tops.
That and Big Stig.
Thank GOD for Bittorrent.
C’mon, they had an Apache helicopter trying to get a firing lock on a maneuvering Lotus Elige! They put a Toyota truck on the top story of a building implosion, then drove it off the rubble into the studio! They made a car gun to destroy caravans! They find some of the most badass, fastest cars and they pull worldwide instead of sticking with just one country’s cars. The Stig is awesome. They always seem to be having so much fun that only a churl would badmouth the show.
Top Gear kicks ALL the ass… 
They drove to the magnetic north pole!
God, yes! That was pretty much the awesomest thing I’ve ever seen on TV.
Rather like why I enjoyed being taken to watch stock car (and that’s the British ones, short oval & full contact) and banger races (even more so) long before I had any understanding or need to know what it felt like to drive a car.
Things Going Bang.
Things Smashing Into Other Things.
Things Crashing in a Humourous Way.
Caravans Going Bang.
There’s a gradual refinement (not the right word, of course) along these lines, which Top Gear has pursued further than anybody else. And while they’ve mostly abandoned covering real cars, the power laps are still only for road-legal cars, and manufacturers are more than willing to provide cars to be pitted against the current rankings. Except Bugatti, who have never let them put a Veyron around the track, terrified either that it would get wrecked or that it wouldn’t make the top, you decide.
AND Drunk Gin and Tonics while driving…in international waters.
No. They turned a Reliant Robin into a space shuttle
(well, they turned a Reliant Robin into a hole in the ground, actually, but with style)
It’s the things like:
Give Jeremy Clarkson the fastest car in the world, and let him race it from Italy against James May and Richard Hammond in a Cessna.
Jeremy Clarkson driving a DB9 down a French Motorway racing May and Hammond in the HGV, with the gendarmes telling him to go faster.
The really genuine level of public concern and relief when Richard Hammond crashed the dragster and recovered.
Top Gear achieves a level of celebrity with three guys just being who they are - blokes. It really is not forced or hyped, and the public really like it.
Si