Interesting point, Lord Thag! I'm surprised I never thought of that before.
Come to think of it, it can be applied even more to handhelds:
Gameboy destroyed all competition for an entire decade, despite being in black and white! Lynx was the first to step up against it and was far more technologically imrpessive, but didn't have a chance. Turbo Express, Game Gear (though did well enough on it's own), Nomad, Neo Geo Pocket, Game.com; none of them could stop it.
Gameboy Color beat out Neo Geo Pocket Color by a long shot, though I'm not sure if the NGPC was any more powerful (I always thought it was personally).
By the time of Gameboy Advance, I guess other companies realized there wasn't much of a chance of taking away the crown from the Gameboy series. So uhh, I guess you could say N-Gage here? Wonderswan Color maybe?
Nintendo DS is constantly breaking sales records, despite being known for being less powerful than PSP.