OneLoad64 Games Collection by StatMat, is a huge 2000+ collection of games presented as single files, which makes it pretty easy to store on any type of large format media storage such as an SD2IEC, TapeCart, BackBit, KungFu Flash, etc.  To find out more about the history of this collection and for a full listing of the games included, check out this post on the Lemon64 forum.