Actually there is a difference. I can buy PS3 games at amazon or any other retailer. No one is forcing devs to sell games on PSN, that is their choice.
Seriously? People can't read? I said ARCADE GAMES!!! Please tell me where else I can buy Arcade games!?? Unless I am mistaken (possible and if so I will take back what I say) you can only buy arcade games from the console manufacturers store. From what I can tell I made it pretty obvious what I was talking about. Though it seems people don't want to read.
I just searched Amazon for some Play Station Network Arcade Games. Haven't found any listed to buy somehow via Amazon yet.
Just did the same for the 360 Arcade Games. Nothing. Oh just did the same for 360 Indie Store. Nothing. I can only buy those games from the store Microsoft Controls.
Again...please try to read the post.
Some developers do not get the licenses to develop an official disk game for those systems. Some developers can only develop Arcade Titles. From what I can tell from doing a lot of Googling I can't buy these anywhere else unless I get it from the Console Manufactures Store.