You have a link? I've read a bit of C.S. Lewis and would be a bit surprised if he made such a direct statement.
In one place, I believe in Mere Christianity, he's talking about Christianity as being the only religion that combines two types of religion - like two types of soup, he says, clear and thick. "Thick" religions are the type with local associations and ecstatic rites and physical practices -- "clear" religions are the philosophical, ethical, moral ones. And, he adds, Christianity mediates between the two, it tells a West African convert from animism that he must obey the ethical law, and "it tells a twentieth-century prig like me to go fasting to a mystery - to take the body and blood of the Lord." (That quote is close; my Lewis books are upstairs.)
On another occasion, he's talking about going to church and instead of focussing on the service thinking about the guy in the next pew with squeaky boots or the grocer who hands you the program. Then he says, "Except for the Blessed Sacrament, the holiest object presented to your senses is your neighbor."
He refers to the Real Presence on other occasions, but those are the best examples I can give from memory.