There may be good games under 50 megabytes. Either because they are really low requirements, made for a contest/jam, or whatever.
I had another idea for avoid the oversaturation a bit is to not allowing constant uploads. For example, only be able to upload a maximum o 2 new projects per month or having a 'launching window' for example, only all days between the 1º and 10º day of every months can be used to upload new projects. My idea is not so much as 'quality control' (because quality can be subjective) but to 'disincentivize' spam, by making it cumbersome.