I think Wikipedia describes it well enough:
Each ride is given a set number of points per voter (for instance, 1 to 10. I'm not sure what it really is). So far, so good.
Though, while Mitch Hawker and the old ForceFactor system on CF was based on averages, the Golden Tickets are based on total score. This can - and does - favour American rides over rides anywhere else, regardless on how individuals rate the rides.
Say you've got a group of ten American enthusiasts going to Japan to ride the new coaster at Wacky Animestuffland, the Polkadot Express. The ride blows them all out of the water. With eyes running with tears of joy, and their intestines pressed up their throats because of all the airtime, they submit their ballots to the Golden Tickets. They all agree the Polkadot Express deserve a flat 10. None over, none at the side. It simply is the best coaster anybody have ever ridden anywhere. However, few if any Japanese have ever heard about the Golden Tickets, never mind being eligible to vote, so the Polkadot Express only gets those ten 10's.
Meanwhile, at Bald Eagle Tycoonworld in the US, the new Superman Batman Spiderman Spinecrusher 3000 (C)(R)[super]TM[/super] has opened. Pretty much anybody who rides it think it's a pile of total garbage. It rearranges the disks in your lower back, gives you a concussion and explosive diharrea, and plays Bieber at full volume in the queue. A hundred and ten eligible Golden Ticket voters all give it an unanimous 1.
This leaves the Polkadot Express with 100 points, as opposed to the Spinecrusher's 110. The Spinecrusher then wins, and Bald Eagle Tycoonworld is celebrated as the park with the best coaster ever, at least better than the crap they're building in Japan.
So the system isn't rigged. It's just incredibly flawed, giving the parks visited by the most eligible voters a clear advantage over anything else. If the park lies off the beaten track, it's almost guaranteed to fail. On the other hand, if the park is visited by enough people, you can build anything and still win. Wich clearly happens every year.