Both rappers are literally 8 and 9 in my top 10 of all time rappers, with Ice Cube taking the higher spot.
Both are great MC's but they both strive to do different things, I think they are both equally great at telling stories, but Ice Cube does so in minimalist way, getting straight to the point where as Ghostface actually paints in watercolors with his words crafting a world around you.
Discography at this point, taking in their complete works, I may actually have to give to Ghostface. I don't know if he is the type of rapper whose discography has the impact of Ice Cube's 1st 3 in terms of impact on the culture and on other rapper's in general but I'll say this though in favor of Ghost, even Ghost's less than stellar albums have had brilliant moments, and his fall off is a lot less dramatic. Ice Cube has dropped a couple of duds. Quotables are kind of subjective but I think it's a wash, just depends on what you look for in a great verse.
I think if Ghost drops one more really good album, I would give him the nod.
I will also add this Cube's best 3 albums are better than Ghost's best 3 but Ghost worst 3 are better than Cube's worst 3 (by a considerable margin).
Actually after typing this, I may have to rethink this.