Newton
PowerPC
Apple TV
.....
(the Flash-less) iPad
But he has failed, too.... Perhaps if he had opened up way back when, Apple would have been bigger than MS....
Newton -> failed because the concept was more ambitious than the hardware/software at the time could support. Even then, it was adapting to the user [ie, learning your handwriting], rather than Palm's idea of you adapting to the device [their wacky script]. This was the same as QuickDraw GX, WAY more advanced graphics system than anything else, but the available hardware to make it run was just too expensive [it needed lots of RAM at a time when RAM was rather expensive], and Taligent [I think that's the cross-platform name, there was another name that Apple used, but I can't think of it], where you had basically a blank slate, and you build a document by adding containers to it [of a variety of content], also really RAM-hungry (and complicated to program).
PowerPC -> failed how? While Apple was selling PowerPC systems [particularly after the 'cloning' debacle], Apple was consistently gaining market share each year, selling millions of computers each quarter. There are a lot of PC manufacturers that wish they could sell as many systems now each year that Apple was selling 10 years ago. Apple had to bail to Intel because IBM wasn't interested in furthering PowerPC chips for desktops and laptops, just for their servers and higher end workstations.
Apple TV -> failed how? Over 3 years, they've sold over 6.6 million of them. Again, there are LOTS of media devices that are made to connect to TV's that their manufacturers WISH sold that well.
Hell, Analysts are expecting Apple to sell what, 10 million iPads in the first year. That probably is more than all the kindles [of all versions] than Amazon will have sold, and Amazon has had an extra year of sales. There's a reason why Amazon isn't saying how many Kindles they are selling....and why they were offering a 100% money back [and you keep the kindle] guarantee during January to their customers before the iPad was announced.