The question about the failure rate is a little more complex with the Xbox 360 than the other two consoles.
Namely because in different regions there are different hardware parts that are to blame.
In the European region for example, a larger percentage of the failure rates are due to the DVD-Drive (which was originally Panasonic and since changed to Samsung) where-as in the North American region is was more down to cut-corners on costs of the Northbridge that while would effectively burn itself out... this was made worse by the Northbridge actually including the GPU that generated far more heat than you'd normally expect from a Chipset.
If this wasn't bad enough though, the IBM PowerPC Processor has always had an issue that would cause many consoles all over the world to simply quit working because of IBM being absolutely useless at fabricating working processors.
This issue is present even in the Wii and PS3, it is also the main cause of the PS3's failure rates. Something that is interesting to note is that the issue with the PPC being the cause is so difficult to find when trying to troubleshoot given the fact the first thing to appear to fail is optical/hard disk media. i.e. the persistant memory hardware. As data is being corrupt by the processor itself and the programs then believe it's a media error.
The GameCube showed this perfectly as a HUGE number of the consoles games would apparently become unreadable as soon as it got to hot inside. Yet checking the disc would so no damage, or even fingermarks; and seconds later the section that crashed the console would suddenly work and another section a bit further on would cause the same disc read error.
To be honest, most of the failures past the hardware (that has since been replaced in the Xbox 360, and will see another shift to pure AMD hardware within the next year) are down to environment. Yeah you can claim "well this console is poorly constructed" blah blah
But take this as a good case example:
My friend is currently on his 4th Xbox 360 in 18months, it's kept in his room. He leaves it on all the time, and is a heavy smoker plus it is quite warm in his room without anything on to begin with.
Where-as I've got 3 Xbox 360s, a 20GB Premium (think 2nd Gen), a 1st gen Arcade, and a 1st gen 60GB Premium. None of which have failed, while I smoke heavily too; cause of others in the house I smoke outside, the Xbox is turned off whenever it's not in use and the AC keeps the room it's in quite cool.
The 60gb has been known to freeze after prolonged useage (on my days off I like to have some mammoth gaming sessions) and it is the primarily used console (a good 6-10hours a day total as everyone uses it).
Still in 3 years, none have failed. In-fact the Arcade with a 20GB HDD I did have, was used for about 6months before I sent it to my brother who wanted on last year with that one also going quite strong still.
Sometimes I think it is luck of the draw, but honestly I'm certain it's more down to environment and over-useage. Well that and most people simply send their Xbox 360s back to be "reconditioned" rather than getting a new one.
Personally that's why I got (doubt I'll use it) an extended warrenty from the Game Retailer who have a no quibble replacement policy on all Console Hardware. Pay an extra £10 per year of cover, and if anything goes wrong I just take it back and they hand me a new console. As they've been offering that for almost 3 years now, frankly I doubt the Xbox 360 failure rate is anywhere near as high as Game Informer reckon it is; else they'd be loosing a shedload of money.