The Dreamcast is. Close second would be the PlayStation 1, third Wii, fourth PlayStation 3 and fifth GameCube. Don't own the two Xboxes, PS2 or Saturn so can't judge those. Played the first Xbox some times, but not enough to give a definitive judgment and similarly, WiiU isn't out long enough to judge.
I don't care about any of the PS3's features. I care about the games.
In that area, Dreamcast and PS1 easily win.
-The most reliable system i've ever seen.
Not really, though I've never had a system die on me including the PS3 (magic hands I guess ), I don't dare to keep the PS3 on for too long. My cousin's died and mine makes way too much noise for it's own good. It's also the only console ever I've actually taken apart completely to get all the dust out. All the others (and I own consoles as old as the 2nd gen) didn't need that. In built quality, PS3's definitely the worst I own. On the software side it's bad too, though that's likely to be caused by the heat, but it's frozen up more than it's fair share.
Generally, I feel that the older the console the more reliable it is. Manufacturers get sloppier by the generation in that regard.