I've heard it pointed out before that these kids were living on World War 2 rations and, regardless of the quality of Turkish Delight under normal circumstances, it probably tastes a heck of a lot better when you've been eating mostly meat, cheese, and preserves for the last however long (though in Googling it, I see they did get SOME sweets in rations).
That helps explain why Edmund was initially excited about Turkish delight and called it his favorite. The other thing to remember is that Edmund wasn't actually fed Turkish delight in the book. He was fed snow that the White Witch enchanted. The appearance, taste, and resulting thrall were the effects of the witch's magic. He was actually craving Evil Magic Delight when he betrayed his family (until he was redeemed by Lion Christ's sacrifice of course).
I went to London last month and, by all means, any foreign food would be better than whatever those kids were having.
