There's a lot of of games out there with 4x MSAA already both on 360 and PS3 and it's not because of eDRAM. For example GT5P in 720p mode has 4xMSAA AND running at 60fps.
In fact you can't even fit some 720p+2xmsaa in the 10MB of the Xenos (9.6MB precisely), u have to tile the rendering (multi pass of render). Alan wake doesn't have 4x msaa though (neither Halo Reach), last screen from Remedy are supersampled and there s already a lot of tearing going on according the recent vids of the game.
Here is some facts :








