Question

1. My favorite food is noodle.
2. My favorite food is a noodle.
3. My favorite food is noodles.
(Which one is right?)

4. My favorite food is ramen.
5. I ate two ramens yesterday.
6. I bought three ramens at a supermarket.
(Are they all grammatical? Can we use the plural forms as in the two sentences?)

7. My favorite food is a sandwich.
8. My favorite food is a hamburger.
9. My favorite food is a noodle.
(We have to put 'a' before food names, right?)

10. My favorite food is sushi.
11. My favorite food is cereal.
12. My favorite food is kimchi fried rice.
(We should not put 'a' before food names here, right?)

Answer 1

#s 3, 4, 7, 8, 10, 11, 12 are all correct.

#s 2 and 9 mean one noodle!
http://www.meatlovessalt.com/wp-content/uploads/2014/01/noodle.png

#s 5 and 6 need additional words to make sense -- maybe these:
I ate two bowls of ramen yesterday.
I bought three packages of ramen noodles at the supermarket.

Undoubtedly, this is confusing! English is not easy!