According to this list... It's the PS3. I still don't constitute it as the worst selling console. I think it's still better than the PS4 (Including the vast library of games it has plus 80% or more PS4 games are available on the PS3 as well). I think it's also unfair to put the PS3 into this list also because it's still pumping games and selling consoles as well (Thing is a BEAST)! So I am putting an asterisk (*) on the PS3 here.
And seeing the amount of Sega systems here has made me realized how many times it's had it's ass handed to itself each generation (no wonder they are almost obsolete now).
Not counting the PS3. It's definitely the Dreamcast. I could go on and on about the amount of classics it's had. And we are still talking abut Shenmue 3 for a reason. You can point the birth of MMOs to it as well, plus the concept of Destiny is based off of PSO anyway.
And this list should have included the Gamecube and the N64 IMHO.