I mean they design great systems and they make great games, those facts are indisputable. But their track record is one of frustration for the true enthusiast. For every unique approach and inventive idea, Nintendo always manages to work in at least one boneheaded decision.
Original NES - I've got news for you, it wasn't dust that kept your games from reading correctly. It was the goofy loading mechanism they created for the cartridges, where each one had to be slotted into a little spring-loaded elevator before being plunged down into the bowels of the device.
Super Nintendo - It was just awesome, I have nothing bad to say about it. The exception that proves the rule. Moving on.
Nintendo 64* - It was a cartridge based system at a time when everyone knew that disk based media were the way to go. This decision lost Nintendo their relationship with Squaresoft, which is a bit like trying to run a pizza restaurant without any cheese.
Gamecube - Four controller ports, two memory card slots. WHAT.
Wii - Oh sure, it's a neat system that everyone seems to love. But at the same time it's the 64 all over again. All the other systems have hard drives that let developers update their games and push out new content. What does the Wii have? 256 megabytes of flash memory.
And the problem extends into their portable systems too.
Gameboy Advance* - No backlight. Unless you found just the right lighting, you couldn't see the thing. That's not a good feature for a portable device.
Gameboy Advance SP - Finally, you can see your games. Course now you can barely hear them, since there's no headphone jack. A portable device that you can't hook earbuds into. Madness.
Nintendo DS - This is easily one of the ugliest pieces of hardware I've ever seen:
The first time I saw it, I thought it was a joke. It looks like a prototype, not a device for regular consumers.
Nintendo DS Lite - Finally a sleek portable device. Oh but, you know those GBA cartridges? Yeah, now they stick out of the device like a giant, plastic tooth.
Nintendo DSi - They resolved the issue with the carts sticking out! They removed that functionality completely!
*Yet despite everything, these are the only two things on this list that I've never owned. *sigh*