Here you go, gentlemen.  Syscoin seems to have a large edge on the race for a decentralized market mainly due to the fact that everyone else sucks:

Bitbay:  Closed source!  Moderated!  Enough said!

Axis Mundi:  Linux only.  I really don't have the patience to get this crap to work but I am no Linux guru.  This marketplace has no chance of ever going mainstreem with average Joe.  Has arbitrated crap-escrow.

NXT Freemarket:  Massive pre-issued coin, will never use on principle alone, closed source at launch, NXT users can go f@ck themselves, desktop version not working due to "changes in NXT", web version not working either.  Has arbitrated crap-escrow.  

Openbazaar:  Not anonymous.  Does not work over Tor.  Automatically eliminated from consideration.

Bitmarkets:  2-party escrow, works over TOR, but who cares, its OSX.  Automatically eliminated from consideration.

Shadowcash:  Has been de-anonymized in the past but fixed the bug... growing pains?  lead dev doesn't seem very intelligent, probably why they still have nothing workable after 2 years?  Might have potential, the only other possible competitor to Syscoin IMO but I have yet to actually see anything.  Shadowmarket to be release by the end of 2016?  Doubt it.  Has superior 2-Person escrow.  Is the core dev really a 14 year old freckle-faced fat kid???