Do you lie to your friend? Do you?
You go to a friend's for a meal at a party. The friend tells you the food will be great - even maybe tells you something you will have is "legendary" or "famous". You go. You try. The result? Not good! Perhaps even bad. The food is only a legend in the chef's mind. This is your friend. So... when they ask if you like it do you tell? Do you fake it? Do you tell them you dislike it? What do you do?
It depends on how close a friend but, for most, count me in on the sin of omission - I'd never lie but if pressed . . .
'It was very flavorful'
'I've never had anything quite like it'
'Thank you for such putting in such a great effort on my behalf'
'I really need to see the recipe' (to see what went wrong!)
But most likely
'Thank you, I had a wonderful time - you're a great host(ess)'
[Edit - with more thought, the following:
For my friends that are very much into food and they, of course, know the same of me, I'll deconstruct the food while eating (again, only with certain friends) and then start to riff on the ingredients. I'll likely never say anything is bad (but that's me) but will suggest improvements of ingredients or techniques. And I do this because I expect the same of them - my dishes can't improve unless someone gives me feedback. Some of my friends have told me to just start over on the creation of a new dish - and I love them for it]
The people I call friends in this life, are people I have no problem giving and getting honesty from. If a friend asked me how something was, I would tell them what was or wasnt good and maybe what could be better/how. Otherwise, that friend goes on through life thinking this dish is sensational, and serving it with pride to other unsuspecting people. How is that being a friend?
now, just some casual acquaintance? yeah, I tell the white lie and say thank you and leave.
I'd probably ask some probing questions about the food and discuss ways to tinker (though not saying it's bad).
I have a tough time outright lying. You can tell pretty quickly if I am lying. So I don't think I could in this situation, but I would probably choose a tactful response like some already posted above, such as " I had a great time! Thanks so much for inviting me!"
If you think you can pull off a white lie, and it works for you, go for it. And I agree that I don't really need to lie to close friends. If you think your relationship can handle it, ten I think honesty is always best.
"that was a very interesting dish." -- specific to the dish.
thank you for the nice time." -- overall.